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javascriptunary-operator

+ unary operator in javascript

i have read this topic already : Explain +var and -var unary operator in javascript

but i still can't understand this simple code :

var a = 3;
console.log(-a);  // -3
console.log(+a);  //  3
a = -a;
console.log(a);  // -3
console.log(+a);  // -3

"The unary negation operator precedes its operand and negates it."

"The unary plus operator precedes its operand and evaluates to its operand but attempts to converts it into a number, if it isn't already."

but i still can't figure why console.log(+a) return 3 the first time.

Solution

  • but i still can't figure why console.log(+a) return 3 the first time.

    The value of a is 3 at that point.

    The previous line, -a, takes the value of a, negates it and passes it to console.log. It doesn't assign the changed value back to a.