Format a string

Replace {0}, {1}… placeholders with values in order.

JavaScript Version 1.0.0 · MIT · .md

function format({ template, values }) { return values.reduce((text, value, i) => text.replaceAll(`{${i}}`, String(value)), template); }

Input & expected output

{
  "template": "Order {0} ships to {1}",
  "values": [
    "8812",
    "[email protected]"
  ]
}

"Order 8812 ships to [email protected]"

The edge case

{
  "template": "{0}{0}",
  "values": [
    "ab"
  ]
}

"abab"

Know the limits

• Replacements run in order, so a value containing "{1}" is replaced again by the next value. Use a template engine with escaping for HTML.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Capitalize a string — Uppercase the first Unicode code point and preserve the remaining text.
• Reverse a string — Reverse Unicode code points without splitting surrogate pairs.
• Check a palindrome — Compare a string with its code-point reversal.