proposal-iterator-join/spec.html at main · tc39/proposal-iterator-join · GitHub

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<!DOCTYPE html>
<meta charset="utf8">
<pre class="metadata">
title: Proposal Iterator Join
stage: 3
contributors: Kevin Gibbons
</pre>

<div id="metadata-block">
  <h1>Contributing to this Proposal</h1>
  <p>You can discuss this proposal <a href="https://github.com/bakkot/proposal-iterator-join">on GitHub</a>.</p>
</div>

<emu-clause id="sec-iterator.prototype.join">
  <h1>Iterator.prototype.join ( _separator_ )</h1>
  <p>This method converts the values of the iterator to Strings, and then concatenates these Strings, separated by occurrences of the _separator_. If no separator is provided, a single comma is used as the separator.</p>
  <p>It performs the following steps when called:</p>
  <emu-alg>
    1. Let _obj_ be the *this* value.
    1. If _obj_ is not an Object, throw a *TypeError* exception.
    1. Let _iterated_ be the Iterator Record { [[Iterator]]: _obj_, [[NextMethod]]: *undefined*, [[Done]]: *false* }.
    1. If _separator_ is *undefined*, then
      1. Let _sep_ be *","*.
    1. Else,
      1. Let _sep_ be Completion(ToString(_separator_)).
      1. IfAbruptCloseIterator(_sep_, _iterated_).
    1. Set _iterated_ to ? GetIteratorDirect(_obj_).
    1. Let _result_ be the empty String.
    1. Let _first_ be *true*.
    1. Repeat,
      1. Let _value_ be ? IteratorStepValue(_iterated_).
      1. If _value_ is ~done~, return _result_.
      1. If _first_ is *true*, then
        1. Set _first_ to *false*.
      1. Else,
        1. Set _result_ to the string-concatenation of _result_ and _sep_.
      1. If _value_ is neither *undefined* nor *null*, then
        1. Let _valueString_ be Completion(ToString(_value_)).
        1. IfAbruptCloseIterator(_valueString_, _iterated_).
        1. Set _result_ to the string-concatenation of _result_ and _valueString_.
  </emu-alg>
</emu-clause>