javascript - Why does null == undefined evaluate to true? -

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i have code below not clear me

var = null;  if(a==undefined) alert("true"); else  alert("false");

when ran above code alerts true.

can explain whats reason or concept behind this?

it's true because == loose equality operator, , null , undefined loosely equal (null == undefined true). if use strict equality operator, ===, not equal (null === undefined false).

basically, loose equality operator coerce operands if they're of different types (see abtract equality comparison in spec). 0 == "" true, instance, because if coerce "" number, it's 0. strict equality operator considers operands of different types not equal (see strict equality comparison); not coerce.


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