判断伪数组
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
}
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