What is wrong with this JavaScript clear function code?

Question

Why the clear function doesn't work. I am not sure what I am doing wrong? Any help is appreciated. Regards Yusuf

    function StringBuilder(initials) {
      var list = [];
      if (initials) {
        list.push(initials);
      }
      return {
        append: function (str) {
          if (!str) {
            str = "";
          }
          list.push(str);
          return this;
        },
        appendLine: function (str) {
          if (!str) {
            str = "";
          }
          list.push(str + "\n");
          return this;
        },
        clear: function () {
          this.list = [];
          return this;
        },
        toString: function () {
          return list.toString().replace(/,/g, " ");
        }
      };
    }

"doesn't work" is vague. Can you describe specifically what's happening? — jmargolisvt
– jmargolisvt, Commented Apr 7, 2018 at 15:00
Why are you returning this? also please show how you are calling your code. — ngeksyo
– ngeksyo, Commented Apr 7, 2018 at 15:03
@ngeksyo probably so he can write sb.append("hello").append("world") — Pointy
– Pointy, Commented Apr 7, 2018 at 15:04
I saw the issue, on the clear function remove this. in the this.list = [] — ngeksyo
– ngeksyo, Commented Apr 7, 2018 at 15:06

Pointy · Accepted Answer · 2018-04-07 15:02:52Z

2

Your clear() method resets this.list, but list is not an object property; it's a variable in the closure. The code should be just

    clear: function () {
      list = [];
      return this;
    },

answered Apr 7, 2018 at 15:02

Pointy

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4 Comments

Pointy Over a year ago

Also note that list.join("") is a little shorter than calling .toString() and .replace().

Yusuf Celik Over a year ago

Thanks for the hint as well

Yusuf Celik Over a year ago

Also, what is the difference between var sb = new StringBuilder() and var sb = StringBuilder() ?

Pointy Over a year ago

@YusufCelik there is no difference, because your function always returns a new object.

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