分类：javascript

在IE浏览器环境，数组里面的最后一个元素的分隔逗号一定要删除，不然会自动增加一个undefined的数组元素；

今天做项目的时候，无意乱用map方法，chrome和firefox支持，但是IE8不支持，网上找了一下有木有解，发现国外有大神写了array.prototype的map扩展

JS源码：

success:function(res){
    $('#busicode').find('.select-loading').text('请选择');
        res.data.map(function(element){
        $('#busicode').append('<option value="'+element.busicode+'">'+element.businame+'</option>');
    });
}

array.prototype.map方法：

// Production steps of ECMA-262, Edition 5, 15.4.4.19
// Reference: http://es5.github.com/#x15.4.4.19
if (!Array.prototype.map) {
    Array.prototype.map = function(callback, thisArg) {

        var T, A, k;

        if (this == null) {
            throw new TypeError(" this is null or not defined");
        }

        // 1. Let O be the result of calling ToObject passing the |this| value as the argument.
        var O = Object(this);

        // 2. Let lenValue be the result of calling the Get internal method of O with the argument "length".
        // 3. Let len be ToUint32(lenValue).
        var len = O.length >>> 0;

        // 4. If IsCallable(callback) is false, throw a TypeError exception.
        // See: http://es5.github.com/#x9.11
        if (typeof callback !== "function") {
            throw new TypeError(callback + " is not a function");
        }

        // 5. If thisArg was supplied, let T be thisArg; else let T be undefined.
        if (thisArg) {
            T = thisArg;
        }

        // 6. Let A be a new array created as if by the expression new Array(len) where Array is
        // the standard built-in constructor with that name and len is the value of len.
        A = new Array(len);

        // 7. Let k be 0
        k = 0;

        // 8. Repeat, while k < len
        while(k < len) {

            var kValue, mappedValue;

            // a. Let Pk be ToString(k).
            //   This is implicit for LHS operands of the in operator
            // b. Let kPresent be the result of calling the HasProperty internal method of O with argument Pk.
            //   This step can be combined with c
            // c. If kPresent is true, then
            if (k in O) {

                // i. Let kValue be the result of calling the Get internal method of O with argument Pk.
                kValue = O[ k ];

                // ii. Let mappedValue be the result of calling the Call internal method of callback
                // with T as the this value and argument list containing kValue, k, and O.
                mappedValue = callback.call(T, kValue, k, O);

                // iii. Call the DefineOwnProperty internal method of A with arguments
                // Pk, Property Descriptor {Value: mappedValue, : true, Enumerable: true, Configurable: true},
                // and false.

                // In browsers that support Object.defineProperty, use the following:
                // Object.defineProperty(A, Pk, { value: mappedValue, writable: true, enumerable: true, configurable: true });

                // For best browser support, use the following:
                A[ k ] = mappedValue;
            }
            // d. Increase k by 1.
            k++;
        }

        // 9. return A
        return A;
    };
}

参考来源：GO >>

今天看代码的时候遇到一个原生JS的知识点，下图的

this.id.split('-')[1]

/* 
这里的this是点击那个<button></button>整个对象代码
假设点击了第一个default的<button>
this.id = "switcher-default"
this.id.split('-') = [switcher,default]
this.id.split('-')[1] = "default"
*/

原生javascript扩展知识：

getAttribute：取得属性；
setAttribute：设置属性；

a[0].id
//"header"
a[0].className
//"Xman"
a[0].getAttribute('attrName');
//获取attrName的值，例如 title、style、data-XX等
a[0].setAttribute('attrName','value');
/*
设置attrName的值，在value处输入对应的值，这个value是直接覆盖原来的值，如果你设置了style，如果里面已经有一个样式了，你要加个背景就要在原有的值上加上背景的样式。
例：font-size:16px; 增加背景：font-size:16px; background:#ccccccc;
*/

console.log