nonstd

A library of useful features that aren’t currently in the Deno std lib.

StringBuilder

A StringBuilder is a utility that allows for efficient building of a large string. This version loosely models the C#/.NET StringBuilder interface.

To import:

import { StringBuilder } from "https://deno.land/x/deno-nonstd/nonstd/mod.ts";

To use:

let sb = new StringBuilder();

sb.append("some text 1")
  .append("some text 2");

sb.appendLine("Long text 3...")
  .appendLine("Long text 4...");

let text = sb.toString();

The StringBuilder object has a maxCapacity flag which indicates the maximum characters that can be joined together, and a capacity flag that also serves the same purpose, but can be any value lower than maxCapacity.

To set the maxCapacity beyond the default (1 GB), use the constructor thus:

let sb = new StringBuilder(maxCapacityValue);

You can set the soft capacity level to anything lower than the max. The max cannot be changed beyond the constructor. And the capacity value cannot be set lower than the current length, or the current max.

let sb = new StringBuilder();
...
sb.capacity = newCapacityValue;

It is possible to clear the current text and start fresh with the clear() function:

...
sb.clear();

Because the strings aren’t joined until a toString() is called, each previous append() and appendLine() value is still in memory. If you want to undo a number of recent appends, you can do so by passing a number into the clearn(howMany) function thus:

let sb = new StringBuilder();

sb.append("The quick brown")
  .append("fox jumped")
  .appendLine(" the  lazy")
  .appendLine(" red fox.")
  .append(" <THE END> ");

sb.clear(1);  // removes " <THE END> "
sb.clear(2);  // will remove the " the lazy" and " read fox."
sb.clear();   // will remove everything else.

If for any reason it’s important to flatten all the text fragments into a single string, you can do so with the flatten() function:

sb.flatten();

And you can pass a StringBuilder anywhere you might pass a string, including the constructor if you with to initialize from the text of something else.