Here’s the Javascript code:
var _a = _a || [];
Why it uses “||” (logical OR) and “[]” (an empty array) together?
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Here’s the Javascript code:
var _a = _a || [];
Why it uses “||” (logical OR) and “[]” (an empty array) together?
The expression
_a || []will return_aif it is “truthy”, otherwise[](it is short circuiting, so it only evaluates until one of the operands is ‘true’ or they have all been evaluated).This is essentially checking for null. If
_ais null or undefined (or false, but that is not likely in this scenario) then it is initialized to an empty array.