JS中Array对象扩展（一）

1、用于清空数组

Array.prototype.clear = function() {
    this.length = 0;
}

2、判断数据项在数组中的位置

var oldArrayIndexOf = Array.indexOf;//判断是否原始浏览器是否存在indexOf方法
Array.prototype.indexOf = function(obj) {
    if (!oldArrayIndexOf) {
        for (var i = 0, imax = this.length; i < imax; i++) {
            if (this[i] === obj) {
                return i;
            }
        }
        return -1;
    } else {
        return oldArrayIndexOf(obj);
    }
} 

 3、判断数据项是否在该数组中

Array.prototype.contain = function(obj) {
    return this.indexOf(obj) !== -1;
} 

 4、把数据项添加到指定的位置 

 Array.prototype.insertAt = function(index, obj) {
    if (index < 0) index = 0;
    if (index > this.length) index = this.length;
    this.length++;
    for (var i = this.length - 1; i > index; i--) {
        this[i] = this[i - 1];
    }
    this[index] = obj;
}

 5、返回最有一项数据 

Array.prototype.last = function() {
    return this[this.length - 1];
}

 6、移除数组指定索引的值 

Array.prototype.removeAt = function(index) {
    if (index < 0 || index >= this.length) return;
    var item = this[index];
    for (var i = index, imax = this.length - 2; i < imax; i++) {
        this[i] = this[i + 1];
    }
    this.length--;
    return item;
} 

 7、移除数据项的数据 

Array.prototype.removeAt = function(obj) {
    var index = this.indexOf(obj);
    if (index >= 0)
        this.removeAt(index);
}

 8、用于数组的查询

用于查询对象数组中对象的某些值，同时支持对已查询属性进行重命名，若查询的属性不在改数组中，则该属性返回为undefined

Array.prototype.select = function(args) {
    var newItems = [];
    if (typeof (args) === "object" && arguments.length === 1) {//传入查询的参数为对象时的处理方式
        for (var i = 0, imax = this.length; i < imax; i++) {
            var item = {};
            for (var key in args) {
                if (args[key] !== undefined) {
                    item[key] = this[i][key] === undefined ? "undefined" : this[i][key];
                }
            }
            newItems.push(item);
        }
    } else if (typeof (args) === "string" && arguments.length === 1) {//传入参数为字符串，且只有一个参数的处理方式
        for (var i = 0, imax = this.length; i < imax; i++) {
            var item = {};
            var keys = args.split(',');
            for (var k = 0, kmax = keys.length; k < kmax; k++) {
                var iKey = keys[k].split("as");
                if (iKey.length === 1) {
                    item[iKey[0].trim()] = this[i][iKey[0].trim()] === undefined ? "undefined" : this[i][iKey[0].trim()];
                } else {
                    item[iKey[1].trim()] = this[i][iKey[0].trim()] === undefined ? "undefined" : this[i][iKey[0].trim()];
                }
            }
            newItems.push(item);
        }
    } else {//传入的参数是多个字符串的处理方式
        for (var i = 0, imax = this.length; i < imax; i++) {
            var item = {};
            for (var j = 0, jmax = arguments.length; j < jmax; j++) {
                if (arguments[j] !== undefined) {
                    var iKey = arguments[j].split("as");
                    if (iKey.length === 1) {
                        item[iKey[0].trim()] = this[i][iKey[0].trim()] === undefined ? "undefined" : this[i][iKey[0].trim()];
                    } else {
                        item[iKey[1].trim()] = this[i][iKey[0].trim()] === undefined ? "undefined" : this[i][iKey[0].trim()];
                    }
                }
            }
            newItems.push(item);
        }
    }
    return newItems;
} 

假设数据对象数组为：var obj = [{ name: "张三", second.age: "24", sex: "男" }
, { name: "张二", age: "21", sex: "女" }
, { name: "张一", age: "23", sex: "男" }
, { name: "张四", age: "25", sex: "女" }
, { name: "张五", age: "22", sex: "男"}];

例一：obj.select("name,second.age as age,sex");
例二：obj.select("name","second.age as age","sex");
例三：查询属性对象var arg={name:"",second.age:"",sex:""};
obj.select(arg);