Thông tin tài liệu
CD-442 Part VI ✦ Appendixes Listing 19-11 (continued) document.all.counter.innerText = i } // BEGIN UNDO BUFFER CODE // buffer global variables var newRanges = new Array() var origSearchString // store original search string and bookmarks of each replaced range function pushUndoNew(rng, srchString, replString) { origSearchString = srchString rng.moveStart(“character”, -replString.length) newRanges[newRanges.length] = rng.getBookmark() } // empty array and search string global function clearUndoBuffer() { document.all.counter.innerText = “0” origSearchString = “” newRanges.length = 0 } // perform the undo function undoReplace() { if (newRanges.length && origSearchString) { for (var i = 0; i < newRanges.length; i++) { rng.moveToBookmark(newRanges[i]) rng.text = origSearchString } document.all.counter.innerText = i clearUndoBuffer() } } </SCRIPT> </HEAD> <BODY> <H1>TextRange.findText() Method</H1> <HR> <FORM> <P>Enter a string to search for in the following text: <INPUT TYPE=”text” NAME=”searchString” SIZE=20 VALUE=”Law”> <INPUT TYPE=”checkbox” NAME=”caseSensitive”>Case-sensitive <INPUT TYPE=”checkbox” NAME=”wholeWord”>Whole words only</P> <P>Enter a string with which to replace found text: <INPUT TYPE=”text” NAME=”replaceString” SIZE=20 VALUE=”legislation”></P> <P><INPUT TYPE=”button” VALUE=”Search and Replace (with prompt)” onClick=”sAndR(this.form)”></P> <P><INPUT TYPE=”button” VALUE=”Search, Replace, and Count (no prompt)” onClick=”sAndRCount(this.form)”> TextRange.findText() CD-443 Appendix F ✦ Examples from Parts III and IV <SPAN ID=”counter”>0</SPAN> items found and replaced.</P> <P><INPUT TYPE=”button” VALUE=”Undo Search and Replace” onClick=”undoReplace()”></P> </FORM> <DIV ID=”rights”> <A NAME=”article1”> <H2>ARTICLE I</H2> </A> <P> Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances. </P> [The rest of the text is snipped for printing here, but it is on the CD-ROM version.] </DIV> </BODY> </HTML> Having a search and replace function available in a document is only one-half of the battle The other half is offering the facilities to undo the changes. To that end, Listing 19-11 includes an undo buffer that accurately undoes only the changes made in the initial replacement actions. The undo buffer stores its data in two global variables. The first, origSearchString, is simply the string used to perform the original search. This variable is the string that has to be put back in the places where it had been replaced. The second global variable is an array that stores TextRange bookmarks (see getBookmark() later in this chapter). These references are string values that don’t mean much to humans, but the browser can use them to recreate a range with its desired start and end point. Values for both the global search string and bookmark specifications are stored in calls to the pushUndoNew() method each time text is replaced. A perhaps unexpected action of setting the text property of a text range is that the start and end points collapse to the end of the new text. Because the stored book- mark must include the replaced text as part of its specification, the start point of the current range must be adjusted back to the beginning of the replacement text before the bookmark can be saved. Thus, the pushUndoNew() function receives the replacement text string so that the moveStart() method can be adjusted by the number of characters matching the length of the replacement string. After all of the bookmarks are stored in the array, the undo action can do its job in a rather simple for loop inside the undoReplace() function. After verifying that the TextRange.findText() CD-444 Part VI ✦ Appendixes undo buffer has data stored in it, the function loops through the array of book- marks and replaces the bookmarked text with the old string. The benefit of using the bookmarks rather than using the replacement function again is that only those ranges originally affected by the search-and-replace operation are touched in the undo operation. For example, in this document if you replace a case-sensitive “states” with “States” two replacements are performed. At that point, however, the document has four instances of “States,” two of which existed before. Redoing the replacement function by inverting the search and replace strings would convert all four back to the lowercase version — not the desired effect. getBookmark() NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ Example Listing 19-11 earlier in this chapter shows how the getBookmark() method is used to preserve specifications for text ranges so that they can be called upon again to be used to undo changes made to the text range. The getBookmark() method is used to save the snapshots, while the moveToBookmark() method is used during the undo process. inRange(otherRangeRef) NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ Example Use The Evaluator (Chapter 13) to see the inRange() method in action. The follow- ing statements generate two distinct text ranges, one for the myP paragraph ele- ment and the other for the myEM element nested within. a = document.body.createTextRange() a.moveToElementText(myP) b = document.body.createTextRange() b.moveToElementText(myEM) TextRange.inRange() CD-445 Appendix F ✦ Examples from Parts III and IV Because the myP text range is larger than the other, invoke the inRange() method on it, fully expecting the return value of true a.inRange(b) But if you switch the references, you see that the larger text range is not “in” the smaller one: b.inRange(a) isEqual(otherRangeRef) NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ Example Use The Evaluator (Chapter 13) to try the isEqual() method. Begin by creating two separate TextRange objects, one for the myP element and one for myEM. a = document.body.createTextRange() a.moveToElement(myP) b = document.body.createTextRange() b.moveToElement(myEM) Because these two ranges encompass different sets of text, they are not equal, as the results show from the following statement: a.isEqual(b) But if you now adjust the first range boundaries to surround the myEM element, both ranges are the same values: a.moveToElement(myEM) a.isEqual(b) move(“unit”[, count]) NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ TextRange.move() CD-446 Part VI ✦ Appendixes Example Use The Evaluator (Chapter 13) to experiment with the move() method. To see how the method returns just the number of units it moves the pointer, begin by creating a text range and set it to enclose the myP element: a = document.body.createTextRange() a.moveToElementText(myP) Now enter the following statement to collapse and move the range backward by 20 words. a.move(“word”, -20) Continue to click the Evaluate button and watch the returned value in the Results box. The value shows 20 while it can still move backward by 20 words. But eventu- ally the last movement will be some other value closer to zero. And after the range is at the beginning of the BODY element, the range can move no more in that direc- tion, so the result is zero. moveEnd(“unit“[, count]) moveStart(“unit”[, count]) NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ Example Use The Evaluator (Chapter 13) to experiment with the moveEnd() and moveStart() methods. Begin by creating a text range and set it to enclose the myEM element: a = document.body.createTextRange() a.moveToElementText(myEM) To help you see how movements of the pointers affect the text enclosed by the range, type a into the bottom text box and view all the properties of the text range. Note especially the htmlText and text properties. Now enter the following statement to move the end of the range forward by one word. a.moveEnd(“word”) TextRange.moveEnd() CD-447 Appendix F ✦ Examples from Parts III and IV Click on the List Properties button to see that the text of the range now includes the word following the EM element. Try each of the following statements in the top text box and examine both the integer results and (by clicking the List Properties button) the properties of the range after each statement: a.moveStart(“word”, -1) a.moveEnd(“sentence”) Notice that for a sentence, a default unit of 1 expands to the end of the current sen- tence. And if you move the start point backward by one sentence, you’ll see that the lack of a period-ending sentence prior to the myP element causes strange results. Finally, force the start point backward in increments of 20 words and watch the results as the starting point nears and reaches the start of the BODY: a.moveStart(“word”, -20) Eventually the last movement will be some other value closer to zero. And as soon as the range is at the beginning of the BODY element, the range can move no more in that direction, so the result is zero. moveToBookmark(“bookmarkString”) NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ Example Listing 19-11 earlier in this chapter shows how to use the moveToBookmark() method to restore a text range so that changes that created the state saved by the bookmark can be undone. The getBookmark() method is used to save the snap- shots, while the moveToBookmark() method is used during the undo process. moveToElementText(elemObjRef) NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ TextRange.moveToElement() CD-448 Part VI ✦ Appendixes Example A majority of examples for other TextRange object methods in this chapter use the moveToElementText() method. Listings 19-10 and 19-11 earlier in this chapter show the method within an application context. moveToPoint(x, y) NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ Example Use The Evaluator to see the moveToPoint() method in action. Begin by creating a text range for the entire BODY element: a = document.body.createTextRange() Now, invoke the moveToPoint() method to a location 100, 100, which turns out to be in the rectangle space of the Results textarea: a.moveToPoint(100,100) If you type a into the bottom text box and view the properties, both the htmlText and text properties are empty because the insertion point represents no visible text content. But if you gradually move, for example, the start point backward one character at a time, you will see the htmlText and text properties begin to fill in with the body text that comes before the TEXTAREA element, namely the “Results:” label and the <BR> tag between it and the TEXTAREA element. Enter the following statement into the top text box and click the Evaluate button several times. a.moveStart(“character”, -1) Enter a into the bottom text box after each evaluation to list the properties of the range. parentElement() NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ TextRange.parentElement() CD-449 Appendix F ✦ Examples from Parts III and IV Example Use The Evaluator (Chapter 13) to experiment with the parentElement() method. Begin by setting the text range to the myEM element: a = document.body.createTextRange() a.moveToElementText(myEM) To inspect the object returned by the parentElement() method, enter the follow- ing statement in the lower text box: a.parentElement() If you scroll down to the outerHTML property, you see that the parent of the text range is the myEM element, tag and all. Next, extend the end point of the text range by one word: a.moveEnd(“word”) Because part of the text range now contains text of the myP object, the outerHTML property of a.parentElement() shows the entire myP element and tags. pasteHTML(“HTMLText”) NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ Example Use The Evaluator (Chapter 13) to experiment with the pasteHTML() method. The goal of the following sequence is to change the <EM> tag to a <SPAN> tag whose STYLE attribute sets the color of the original text that was in the EM element. Begin by creating the text range and setting the boundaries to the myEM element: a = document.body.createTextRange() a.moveToElementText(myEM) While you can pass the HTML string directly as a parameter to pasteHTML(),stor- ing the HTML string in its own temporary variable may be more convenient (and more easily testable), such as: b = “<SPAN STYLE=’color:red’>” + a.text + “</SPAN>” TextRange.pasteHTML() CD-450 Part VI ✦ Appendixes Notice that we concatenate the text of the current text range, because it has not yet been modified. Now we can paste the new HTML string into the current text range a.pasteHTML(b) At this point the EM element is gone from the object model, and the SPAN element is in its place. Prove it to yourself by looking at the HTML for the myP element: myP.innerHTML As noted earlier, the pasteHTML() method is not the only way to insert or replace HTML in a document. This method makes excellent sense when the user selects some text in the document to be replaced, because you can use the document.selection.createRange() method to get the text range for the selec- tion. But if you’re not using text ranges for other related operations, consider the other generic object properties and methods available to you. select() NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ Example See Listing 19-11 earlier in this chapter for an example of the select() method in use. setEndPoint(“type”, otherRangeRef) NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ ✓ Example Use The Evaluator to experiment with the setEndPoint() method. Begin by creat- ing two independent text ranges, one for the myP element and one for myEM: a = document.body.createTextRange() a.moveToElementText(myP) b = document.body.createTextRange() b.moveToElementText(myEM) TextRange.setEndPoint() CD-451 Appendix F ✦ Examples from Parts III and IV Before moving any end points, compare the HTML for each of those ranges: a.htmlText b.htmlText Now, move the start point of the a text range to the end point of the b text range: a.setEndPoint(“StartToEnd”, b) If you now view the HTML for the a range, a.htmlText you see that the <P> tag of the original a text range is nowhere to be found. This demonstration is a good lesson to use the setEndPoint() method primarily if you are concerned only with visible body text being inside ranges, rather than an ele- ment with its tags. TextRectangle Object Properties bottom left right top NN2 NN3 NN4 NN6 IE3/J1 IE3/J2 IE4 IE5 IE5.5 Compatibility ✓✓ Example Listing 19-12 lets you click one of four nested elements to see how the TextRectangle is treated. When you click one of the elements, that element’s TextRectangle dimension properties are used to set the size of a positioned ele- ment that highlights the space of the rectangle. Be careful not to confuse the visible rectangle object that you see on the page with the abstract TextRectangle object that is associated with each of the clicked elements. TextRectangle.bottom . CD-442 Part VI ✦ Appendixes Listing 19-11 (continued) document.all.counter.innerText = i } // BEGIN UNDO. prompt)” onClick=”sAndRCount(this.form)”> TextRange.findText() CD-443 Appendix F ✦ Examples from Parts III and IV <SPAN ID=”counter”>0</SPAN> items found and replaced.</P> <P><INPUT. collapse to the end of the new text. Because the stored book- mark must include the replaced text as part of its specification, the start point of the current range must be adjusted back to the beginning
Ngày đăng: 06/07/2014, 06:20
Xem thêm: JavaScript Bible, Gold Edition part 196 ppt, JavaScript Bible, Gold Edition part 196 ppt
