兼容IE8的方法函数

兼容IE8 数组的 forEach

if ( !Array.prototype.forEach ) {
    Array.prototype.forEach = function forEach( callback, thisArg ) {
        var T, k;
        if ( this == null ) {
               throw new TypeError( "this is null or not defined" );
        }
        var O = Object(this);
        var len = O.length >>> 0; 
        if ( typeof callback !== "function" ) {
            throw new TypeError( callback + " is not a function" );
        }
        if ( arguments.length > 1 ) {
            T = thisArg;
        }
        k = 0;
        while( k < len ) {
            var kValue;
            if ( k in O ) {
                kValue = O[ k ];
                callback.call( T, kValue, k, O );
            }
            k++;
        }
    };
}

兼容IE8 数组的 indexOf

if ( !Array.prototype.indexOf ) {
    Array.prototype.indexOf = function( elt /*, from*/ ) {
        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;
    };
}

兼容bind函数

if ( !Function.prototype.bind ) {
    Function.prototype.bind = function() {
        if ( typeof this !== 'function' ){
            throw new TypeError('Function.prototype.bind - what is trying to be bound is not callable');
        }
        var _this = this;
        var obj = arguments[0];
        var ags = Array.prototype.slice.call( arguments, 1 );
        return function() {
            _this.apply( obj,ags );
        };
    };
}

兼容IE8的getElementsByClassName函数

if ( !document.getElementsByClassName ) {
    document.getElementsByClassName = function ( className, element ) {
        var children = ( element || document ).getElementsByTagName('*');
        var elements = new Array();
        for ( var i = 0; i < children.length; i++ ) {
            var child = children[i];
            var classNames = child.className.split(' ');
            for ( var j = 0; j < classNames.length; j++ ) {
                if ( classNames[j] == className ) {
                    elements.push(child);
                    break;
                }
            }
        }
        return elements;
    };
}

兼容IE8的addEventListener函数

function addEventListener( ele,event,fn ){
    if( ele.addEventListener ) {
        ele.addEventListener( event, fn, false );
    } else {
        ele.attachEvent( 'on'+event, fn.bind(ele) );
    }
}