Instructions for using the javascript indexOf function_Basic knowledge

Usage: strObj.indexOf(str,startIndex[optional])

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where strObj is a required option. String object or text.
str is required. The substring to find in the String object.
startIndex is optional. This integer value indicates the position within the String object to start searching, starting at 0. If omitted, the search is from the beginning of the string.


Note: indexOf for JavaScript is case-sensitive.

The indexOf function method in JavaScript returns an integer value indicating the starting position of the substring within the String object. If the string is not found, -1 is returned. If startindex is negative, startindex is treated as zero. If it is greater than the largest character position index, it is treated as the largest possible index.

The indexOf function performs searches from left to right.
The following example illustrates the usage of the indexOf function method.

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var str1="fdiejDIFADF";
var str="e";
var i=str1.indexOf(str);
alert(i );



As mentioned before, indexOf is case-sensitive. Sometimes this causes us some trouble, so how to solve it? ? Of course, the easiest way is to convert the characters to uppercase or lowercase using toLowerCase or toUpperCase.
The code is as follows:

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The following method uses regular expressions to extend indexOf (from the Internet)

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The following extension is more powerful. It is compatible with the original indexOf function and can also ignore the size. Find (also from the web).

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<script> <BR>var Str = 'ABCDEF'; <BR>var Str1 = 'bcd'; <BR>alert(Str.toLowerCase().indexOf(Str1.toLowerCase())); <BR>str2 = 'AbCdEf'; <BR>alert(Str2.toLowerCase().indexOf(Str1.toLowerCase())); <BR></script><script> <BR>String.prototype.indexOf = function(f,m){ <BR>var mm = (m == false) ? "i":""; <BR>var re = eval("/"+ f +"/"+mm); <BR>var rt = this.match(re); <BR>return (rt == null) ? -1:rt.index; <BR>} <BR>var test = "absnegKIugfkalg"; <BR>alert(test.indexOf("kiu",false)); <BR></script> <script> <BR>String.prototype._indexOf = String.prototype.indexOf; <BR>String.prototype.indexOf = function() <BR>{ <BR> if(typeof(arguments[arguments.length - 1]) != 'boolean') <BR> return this._indexOf.apply(this,arguments); <BR> else <BR> { <BR> var bi = arguments[arguments.length - 1]; <BR> var thisObj = this; <BR> var idx = 0; <BR> if(typeof(arguments[arguments.length - 2]) == 'number') <BR> { <BR> idx = arguments[arguments.length - 2]; <BR> thisObj = this.substr(idx); <BR> } <br><br> var re = new RegExp(arguments[0],bi?'i':''); <BR> var r = thisObj.match(re); <BR> return r==null?-1:r.index + idx; <BR> } <BR>} <BR>alert("bcssssasdfsdf".indexOf('A',3,true)); <BR>alert("bcssssasdfsdf".indexOf('a',3)); <BR></script>