经典JS

//用apply把document当作this传入getId函数，帮助“修正”this;
document.getElementById = (function (func) {
    return function () {
        return func.apply(document, arguments);
    }
})(document.getElementById);

//调用
var getId = document.getElementById;
var div = getId(‘div2‘);


//函数判断

var Type = {};

for (var i = 0, type; type = [‘String‘, ‘Array‘, ‘Number‘][i++];) {

    (function (type) {
        Type[‘is‘ + type] = function (obj) {
            return Object.prototype.toString.call(obj) === ‘[object ‘ + type + ‘]‘;
        }
    })(type);

};