check variable is a array or object

function isArray(o) {
  return Object.prototype.toString.call(o) === ‘[object Array]’;
}

引用

The Miller Device
The JavaScript language currently does not provide a good way to distinguish between objects and arrays. The typeof operator is broken: It identifies arrays as objects. Comparing a value’s constructor property doesn’t work because arrays created in a different frame will have a different constructor. There are do-it-yourself tests for arrayness, but they are complicated and unreliable.
Mark Miller of The Google, by closely reading the ECMAScript standard, has discovered a simpler, more reliable test.
Object.prototype.toString.apply(value) === ‘[object Array]’

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