Javascript Prototype

Resources

• Video on Javascript Prototype

Questions

Q: Create “native” methods

• define a repeatify function on the String object
  • function accepts an integer for how many times the string should repeat
  • returns the string repeated the number of times specified
  • 'hello'.repeatify(3) => hellohellohello

String.prototype.repeatify =
  String.prototype.repeatify ||
  function (times) {
    var str = '';

    for (var i = 0; i < times; i++) {
      str += this;
    }
    return str;
  };

Call "hello".addCommas() and have it put commas between every letter

String.prototype.addCommas =
        String.prototype.addCommas ||
        function () {
          return [...this].join(",");
        };

console.log("hello".addCommas()); // "h,e,l,l,o"


// Last comma removed
String.prototype.addCommas2 =
        String.prototype.addCommas2 ||
        function () {
          const arrayWithCommas = [...this].join(",").split("");
          arrayWithCommas.splice(arrayWithCommas.lastIndexOf(","), 1);
          return arrayWithCommas.join("");
        };

console.log("hello".addCommas2()); // "h,e,l,lo"

Question is testing

• knowledge of inheritance in JavaScript and the prototype property
• ability to extend native data type functionalities (although this should not be done)
• bonus for not overriding previously defined functions
  • testing that the function didn’t exist before defining your own