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Strings and regular expressions

Template literals, common string methods, splitting and joining, and regular expressions.

Runs in Zerethon IDE · Node.js 22 Official JavaScript documentation ↗
main.js 
const name = 'Ada Lovelace';
console.log(`${name} has ${name.length} characters`);
console.log(name.toUpperCase(), name.slice(0, 3), name.indexOf('Love'));
console.log('  padded  '.trim() + '|', '7'.padStart(3, '0'));
console.log('a,b,c'.split(','), ['x', 'y'].join('-'));
console.log('a-b-c'.replaceAll('-', '+'), name.startsWith('Ada'), name.includes('love'));

const text = 'Order 12 shipped, order 7 pending';
console.log(text.match(/\d+/g));
const m = text.match(/order (\d+) pending/);
console.log(m ? m[1] : 'no match');
console.log(/^[\w.]+@\w+\.\w+$/.test('ada@example.com'));

Output

Ada Lovelace has 12 characters
ADA LOVELACE Ada 4
padded| 007
[ 'a', 'b', 'c' ] x-y
a+b+c true false
[ '12', '7' ]
7
true
  • Strings cannot be changed in place; methods return new strings.
  • replace() with a string changes only the first match — use replaceAll() or a regex with the g flag.
  • match() returns null when nothing matches; check before indexing.

Related topics

Official references