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Strings in JS have dozens of methods but in practice you'll use ten of them. They are all functions that don't modify the original string (strings are immutable) but return a new value.

Length, case, search

'JavaScript'.length; // 10
'JavaScript'.toUpperCase(); // 'JAVASCRIPT'
'JavaScript'.toLowerCase(); // 'javascript'

'JavaScript'.includes('Script'); // true
'JavaScript'.startsWith('Java'); // true
'JavaScript'.endsWith('!'); // false

'JavaScript'.indexOf('a'); // 1    (first occurrence, from 0)
'JavaScript'.indexOf('zzz'); // -1   (not found)

length is a property (no parentheses), the others are methods — functions invoked with (…).

Extracting portions with slice

slice(start, end) returns the sub-string between the given positions (end excluded). Negative indices count from the end.

'abcdefgh'.slice(0, 3); // 'abc'
'abcdefgh'.slice(3); // 'defgh'   (omitting end = to the end)
'abcdefgh'.slice(-2); // 'gh'      (last two)

Splitting and rejoining

split(separator) divides a string into an array of pieces. The reverse is join(...) on the array:

'rosso,verde,blu'.split(','); // ['rosso','verde','blu']
['rosso', 'verde', 'blu'].join(' | '); // 'rosso | verde | blu'

Replacing

replace changes the first occurrence, replaceAll changes all of them:

'a-b-c'.replace('-', '_'); // 'a_b-c'
'a-b-c'.replaceAll('-', '_'); // 'a_b_c'

Trim: remove whitespace at the edges

trim() removes spaces (and newlines, tabs) at the start and end. Indispensable when you receive input from a form.

'   ciao  '.trim(); // 'ciao'

Try it

Review exercise