higunjan higunjan - 1 year ago 96
Javascript Question

Javascript ORing in variable how it works?

I want to know the process of ORing in javascript variable. I used below code for just testing purpose. I want just know the process behind these ORing in var. I know the process when we are using in if condition. Please any one explain me in details.

var a = a || "2010" || "Gunjan" || 20;
//output 2010

When I console var
then it gives me output like

  1. Why?

  2. How?

  3. Can anyone one explain me background process?

Answer Source

The Logical Operators returns the value of one of the operands, so if the operands returns a non boolean value then the logical operation could return a non boolean value

Logical operators are typically used with Boolean (logical) values. When they are, they return a Boolean value. However, the && and || operators actually return the value of one of the specified operands, so if these operators are used with non-Boolean values, they may return a non-Boolean value.

Also looking at Short-Circuit Evaluation, the OR operator will stop executing of further conditions once one of the operands is true.

Now looking at your condition var a = a || "2010" || "Gunjan" || 20;, since you have used var a, I'm assuming you are declaring the variable a here, so when the RHS is executed a has a value undefined which is falsy so the OR operator executes the second operand which is a string literal 2010 which is a non boolean but truthy value so that is returned as a result of this operations

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