JavaScript Array object extends indexOf() method_javascript tips

Background: Among the standard methods of Array objects in JavaScript, there is no indexOf() method, which can be extended through the following code.

Copy code The code is as follows:

if (!Array.prototype.indexOf) {
Array.prototype.indexOf = function(elt) {
var len = this.length >>> 0;
var from = Number(arguments[1]) || 0;
from = (from < 0) ? Math.ceil(from) : Math.floor(from);
if (from < 0) from = len;
for (; from < len; from ) {
if (from in this && this[from] === elt) return from;
}
return - 1;
};
}