JavaScript variable with pipeline -

JavaScript variable with pipeline -

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what “options = options || {}” mean in javascript? [duplicate] 5 answers

i have found code in javascript creating object. have no thought below code does.

var = || {};

an explanation appreciated.

the first step here understand becomes this:

var a; = || {};

...and var a no-op if a variable has been declared in current scope.

so first part (var a) makes sure a exists variable if doesn't already.

the sec part says: if a has "truthy" value, maintain (don't alter it). if has "falsey" value, assign {} a.

the "falsey" values 0, nan, null, undefined, "", , of course, false. truthy values others.

this works because of javascript's curiously-powerful || (logical or) operator which, unlike other languages, not result in true or false; instead, evaluates left-hand operand and, if that's truthy, takes value result; otherwise, evaluates right-hand operand , uses result.

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