Spring React - Operator =>

I am just learning Spring react, I don't know Javascript very well. I got to code:

componentDidMount: function () {
    client({method: 'GET', path: '/api/employees'}).done(response => {
        this.setState({employees: response.entity._embedded.employees});
    });

There is written:

componentDidMount is the API invoked after React renders a component in the DOM.

I was looking for what Javascript operator => means. But don't found anything.

This is an arrow function.

An arrow function expression (also known as fat arrow function) has a shorter syntax compared to function expressions and lexically binds the this value (does not bind its own this, arguments, super, or new.target). Arrow functions are always anonymous.

You can see a simple example:

var vec = ['a', 'ab', 'abc'];

var test = vec.map(i => i.length);

alert(test); // 1,2,3