+ $ in jquery. How did not only the base $

Question

I have jQuery code where +$(...)used in many places. The code does not work without part +when doing everything $(...).

I could not find any explanation using Google. I would appreciate any advice, if possible.

function calculate() {
  var a = +$('#a').val(); // what is +$ ?
  var b = +$('#b').val();
  var c = b * 108.40;
  //etc
}

Answer 1

+$()- these are actually two operations in which the first is performed $()to capture your input, and then +forces any input value to a number.

Here is a breakdown of what happens:

var valueA = $('#a').val(); // "123"
var numberA = +valueA;      //  123

console.log('valueA is a ' + typeof valueA);   // 'valueA is a string'
console.log('numberA is a ' + typeof numberA); // 'numberA is a number'

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input id="a" value="123"/>

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