Summary of usage methods and problems of indexOf in JavaScript_Basic knowledge

This method is quite useful. There are corresponding implementations in many programming languages, and JavaScript is no exception. However, when I run the following code in IE:

Copy code The code is as follows:

var arr = [1,2,3];
alert(arr.indexOf(1));

But I was prompted "The object does not support this property and method". It runs fine in chrome and ff. So I went to ask Google experts and found that the indexOf method of Array in js was only implemented in js1.6 version. IE7 and 8 only implemented js1.3 version, chrome was js1.7 version, and ff was js1.8. Version. (ie still half a beat slower). I have no choice but to extend it for IE:

Copy the code The code is as follows:

Array.prototype. _indexOf = function(n){
if("indexOf" in this){
return this["indexOf"](n);
}
for(var i=0;iif(n===this[i]){
return i;
}
}
return -1;
};

is used as follows:

Copy code The code is as follows:

var arr = ["1","2","3"];
alert(arr._indexOf("2"));

Here we have extended the Array prototype. In the extension I added the "_" character to the name of the method. I think this is a good habit. When you extend the prototype, it is necessary to mark your extension.
In the _indexOf method, we first determine whether the current Array implements the "indexOf" method. If so, directly call the system method, otherwise it will be traversed.