javascript - What is the benefit of using === operator to test for undefined instead of using == operator? -

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i test whether javascript variable defined or not, using following test:

if (typeof == 'undefined')     = 'default value'

however, have seen many people suggesting safer use following instead:

if (typeof === 'undefined')     = 'default value'

i aware of difference between == , === operators unable understand why typeof == 'undefined' unsafe.

could please scenario in first code example unsafe or lead issues? also, advantages of using latter syntax on first?

i unable understand why typeof == 'undefined' unsafe

it's not unsafe, it's fine. typeof operator guaranteed return string, you'll comparing 2 strings. abstract equality algorithm behave strict equality.


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