Javascript - Logical Operator

About

Logical operator in Javascript

List

  • &&: AND

OR, ||

Returns expr1 if it can be converted to true; otherwise, returns expr2. See Javascript - Boolean (Truthy|Falsy)

expr1 || expr2

Usage Example:

  • Initialization even if it's a null object
x = null;
y = x || "x was null";
console.log(y)

Snippet example:

Example:

console.log('Return expression1')
console.log(true || 'expr2')
console.log(1 || 'expr2')
console.log('s' || 'expr2')
console.log('\n')
console.log('Return expression2')
console.log(false || 'expr2')
console.log(0 || 'expr2')
console.log('' || 'expr2')

&&

  • true && expression always evaluates to expression
  • false && expression always evaluates to false

Therefore, in a statement such as condition && expression, if the condition is true, the element right after && will appear in the output. If it is false, it will be ignored.


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