js判断变量是不是数组

var arr= [1,2,3,4];
function isArray(o) {
    return Object.prototype.toString.call(o)== '[object Array]';
}
console.log(isArray(arr));


//Object.prototype.toString.call([])             '[object Array]'

//Object.prototype.toString.call({})             '[object Object]'

//Object.prototype.toString.call(1)              '[object Number]'

//Object.prototype.toString.call('1')            '[object String]'

//Object.prototype.toString.call(null)           '[object Object]'

//Object.prototype.toString.call(undefined)      '[object Undefined]'