CODEWITHSUNDEEP
javascriptunderscore.js
user3246794
user3246794

Reputation:

Why doesn't underscore prefer typeof in some cases?

Per Crockford's, The Good Parts

typeof is accurate for function, string, number, boolean, and undefined. null and array are both incorrectly reported as object.

So why not use typeof for the cases in which it does work? It is always faster that is why I wonder why it is not preferred in these cases.

Particularly here for function, string and number.

http://underscorejs.org/docs/underscore.html#section-111

  each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp'], function(name) {
    _['is' + name] = function(obj) {
      return toString.call(obj) == '[object ' + name + ']';
    };   });

Upvotes: 0

Views: 150

Answers (1)

SLaks
SLaks

Reputation: 887415

The point of these wrappers is to catch boxed value objects.

typeof new Number(1) === 'object'

Upvotes: 2

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