Method on

src/js/evented.js:4–14

(event, handler, ctx, once = false)

export class Evented {
  on(event, handler, ctx, once = false) {
    if (isUndefined(this.bindings)) {
      this.bindings = {};
    }
    if (isUndefined(this.bindings[event])) {
      this.bindings[event] = [];
    }
    this.bindings[event].push({ handler, ctx, once });

    return this;
  }

  once(event, handler, ctx) {
    return this.on(event, handler, ctx, true);