jQuery 1.4 Source 449 line (Core.js 431 lines), the method to determine whether the function is as follows (the idea comes from Douglas Crockford 's "The Miller Device"):
Isfunction: function( obj ) {
return toString. call(obj) = = "[Object Function]" ;
},
The author of JQuery also makes a partial comment:
Test/unit/core.js for details concerning isfunction. Since version 1.3, DOM methods and functions like alert aren ' t supported. They return False on IE (#2968).
That is, this method does not correctly recognize the DOM method and some functions (such as alert method, etc.) under IE.
Why is that?
<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 transitional//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd "> <ptml xmlns=" http://www.w3.org/1999/xhtml "> <pead> <meta http-equiv=" Content-type "content=" text/html; charset=gb2312 "/> <title> repair jQuery isfunction method bug</title> </pead> <body> <p> Use the typeof operator to detect various methods:</p> <script> Document.writeln (' typeof eval: ' + typeof eval + ' <br> '); Document.writeln (' typeof confirm: ' + typeof confirm + ' <br> '); Document.writeln (' typeof confirm: ' + typeof window.open + ' <br> '); Document.writeln (' typeof alert: ' + typeof alert + ' <br> '); Document.writeln (' typeof Window.alert: ' + typeof Window.alert + ' <br> '); Document.writeln (' typeof document.getElementById: ' + typeof document.getElementById + ' <br> '); Document.writeln (' typeof document.createelement: ' + typeof document.createelement + ' <br> '); </script> <p> test the original Isfunction function method </p> <script> var isfunction = function (FN, name) {return DOCUMENT.WR Iteln (' isfunction (' + name + '): ' + (Object.prototype.toString.call (fn) = = "[Object Function]") + ' <br> '); } isfunction (eval, ' eval '); Isfunction (Confirm, ' confirm '); Isfunction (window.open, ' window.open '); Isfunction (Alert, ' Alert '); Isfunction (Window.alert, ' Window.alert '); Isfunction (document.getElementById, ' document.getElementById '); Isfunction (document.createelement, ' document.createelement '); Isfunction (isfunction, ' isfunction '); </script> <p> Test Repair isfunction function method </p> <script> var isfunction = (function () {return type of document.getElementById = = "Object"? Isfunction = function (FN, name) {try {return Document.writeln, ' isfunction (' + name + '): ' + (/^\s*\bfunction\b/.test (" "+ fn)" + ' <br> '); catch (x) {return Document.writeln (' isfunction (' + name + '): ' + (false) + ' <br> '); }}: ISfunction = function (FN, name) {return Document.writeln (' isfunction (' + name + '): ' + (' [object function] ' = = OBJECT.PR Ototype.toString.call (FN)) + ' <br> '); }; }) () Isfunction (eval, ' eval '); Isfunction (Confirm, ' confirm '); Isfunction (window.open, ' window.open '); Isfunction (Alert, ' Alert '); Isfunction (Window.alert, ' Window.alert '); Isfunction (document.getElementById, ' document.getElementById '); Isfunction (document.createelement, ' document.createelement '); Isfunction (isfunction, ' isfunction '); </script> </body> </ptml>
[Ctrl + A All SELECT Note: If the need to introduce external JS need to refresh to perform]
It will be found that using TypeOf to detect alert, confirm method, and DOM methods under IE shows object, while other browsers display function.
So how to perfect this problem?
- typeof to detect whether a method (for example: document.getElementById) is object and how it is, rewrite the isfunction function;
- How do you rewrite it? A regular judge of the incoming object string ("" + fn), whether the starting position contains a function, namely:/^\s*\bfunction\b/.test ("+ FN").
OK, look at the modified Isfunction function based on the above ideas:
Copy Code code as follows:
var isfunction = (function () {//performance Optimization:lazy function Definition return "object" = = typeof document.g Etelementbyid? Isfunction = function (fn) {try {return/^\s*\bfunction\b/.test ("" + fn);} catch (x) {return false}}: Isfunction = function (fn) {return "[object function]" = = Object.prototype.toString.call (FN) ; };}) ()
Reference reading:
- "Isfunction hacked, iscallable solution"
- isfunction () or IsObject (), which is the question?
- "Lazy Function Definition pattern"
