Protractor locator to find element(s) by value of attribute

locator.attr.js

by.addLocator('attr',
      /**
       * Find element(s), where attribute = value
       * @param {string} attr
       * @param {string} value
       * @param {Element} [parentElement=]
       * @returns {Array.<Element>}
       */
      function (attr, value, parentElement) {
        parentElement = parentElement || document;
        var nodes = parentElement.querySelectorAll('[' + attr + ']');
        return Array.prototype.filter.call(nodes, function (node) {
          return (node.getAttribute(attr) === value);
        });
      });

Example of usage:

expect(element(by.attr('ng-click', 'exampleMethod()')).isDisplayed()).toBe(true);