References

Beginner-friendly references for web development, with live, editable examples.

The JavaScript string.trimStart() method

Method JavaScript All modern browsers Updated
Quick answer

The trimStart() method removes whitespace from the start of a string and returns a new string. " hi ".trimStart() gives "hi ": only the leading spaces go. It's the start-only version of trim(); its counterpart trimEnd() handles the end.

Overview

trimStart() strips whitespace (spaces, tabs, newlines) from the beginning of a string, leaving the end untouched. It returns a new string (strings are immutable), so you use the return value.

It's one of a trio with trim() (both ends) and trimEnd() (the end only). Most of the time you want trim(), but trimStart() is the right tool when trailing whitespace is meaningful, preserving alignment or intentional trailing content while cleaning up leading indentation.

It's occasionally seen under its older alias trimLeft(), which still works and is kept in the spec only for web compatibility; prefer trimStart(). As with the others, it only touches the edges. To remove whitespace inside a string, use a regex replace().

Syntax

str.trimStart()

"  hello  ".trimStart()  // "hello  "

Example

Live example 
<pre id="out" style="font:14px ui-monospace,monospace"></pre>
<script>
  const raw = '    indented line';

  document.getElementById('out').textContent =
    '[' + raw + ']\n' +
    '[' + raw.trimStart() + ']'; // leading spaces removed
</script>

Best practices

  • Use trimStart() when only leading whitespace should go and trailing whitespace matters.
  • For both ends, use trim(); for the end only, trimEnd().
  • Use the return value; the original string is unchanged.
  • Prefer trimStart() over the legacy alias trimLeft().

Frequently asked questions

What does trimStart() do?
It removes whitespace from the start of a string and returns a new string, leaving the end as is.
What is the difference between trimStart() and trim()?
trimStart() removes whitespace only from the beginning; trim() removes it from both ends.
Is trimLeft() the same as trimStart()?
Yes, trimLeft() is a legacy alias. Use the standard trimStart().
How do I trim the end of a string?
Use trimEnd().
string.trimEnd() structuredClone()