类数组

类数组：对象拥有length属性，其它属性（索引）为非负整数的字符串

 

 

类数组判断

变量类型：对象

length: 不能为无穷，不能超过JavaScript数组极限长度的自然数

 

《javascript权威指南》上给出了代码用来判断一个对象是否属于“类数组”。如下：

// Determine if o is an array-like object.// Strings and functions have numeric length properties, but are // excluded by the typeof test. In client-side JavaScript, DOM text// nodes have a numeric length property, and may need to be excluded // with an additional o.nodeType != 3 test.function isArrayLike(o) {
    if (o &&                                // o is not null, undefined, etc.
        typeof o === 'object' &&            // o is an object
        isFinite(o.length) &&               // o.length is a finite number
        o.length >= 0 &&                    // o.length is non-negative
        o.length===Math.floor(o.length) &&  // o.length is an integer
        o.length < 4294967296)              // o.length < 2^32
        return true;                        // Then o is array-like
    else
        return false;                       // Otherwise it is not
}

 

与数组的区别：

     不能直接调用数组的方法，可以通过借用数组的方法，例如  Array.prototype.map.call

类数组对象转化为数组

     1.Array.prototype.slice.call(arguments)  

       2._.toArray()