Unfamiliar use of square brackets in calling a function

Question

In the middle of this page, I find the code below.

var plus = function(x,y){ return x + y };
var minus = function(x,y){ return x - y };

var operations = {
  \'+         


        

Answer 1

operations is an object and when you do operations[property] you will get the associated function and then you are passing the operands as x and y.

operations['+'] is function (x,y){ return x + y } which is plus

operations['-'] is function (x,y){ return x - y } which is minus