Case

> myText.toUpperCase()

Slicing

myText.substr(first, length)
myText.substring(start, end)
myText.slice(start, end)

For using .substr or .slice, see SO thread.

e.g.

> 'abcd'.substr(0,2)
'ab'

> 'abcdef'.substring()
'abcdef'
> 'abcdef'.substring(0)
'abcdef'

> 'abcdef'.substring(1)
'bcdef'
> 'abcdef'.substring(1,3)
'bc'
> 'abcdef'.substring(0,3)
'abc'
> 

> 'abcdef'.slice(1,3)
'bc'

Replace text in text

Replace first occurence only

Replace the first occurence, not a global replace.

Pass first param as a string, not regex.

> 'AAA'.replace('A', 'C')
'CAA'

Or pass regex, but without g:

> 'AAA'.replace(/A/, 'C')
'CAA'

Replace all occurences

A newer method added to JS:

> 'AAA'.replaceAll('A', 'C')
'CCC'

Using regex - note g for global replace.

> 'AAA'.replace(/A/g, 'C')
'CCC'

Or the more verbose:

> 'AAA'.replace(new RegExp("A", "g"), 'C')
'CCC'

You might use RegExp to escape characters for you.

> new RegExp("A", "g")
/A/g
> new RegExp("/A")
/\/A/

Remove empty lines

> myText.replace(/^\n/gm, '');

The Regex pattern finds lines which start with a newline.

The m modified is recommended for multi-line search

Source

If you wanted to just replace a value, you could do:

> myText.replace(/^$/g, 'new value');

Remove whitespace at start and end

  • trim method in MDN docs

    The trim() method removes whitespace from both ends of a string. Whitespace in this context is all the whitespace characters (space, tab, no-break space, etc.) and all the line terminator characters (LF, CR, etc.).

myText.trim();

e.g.

> '   foo  '.trim()
'foo'

Remove only newlines from start and end

source

> myText.replace(/^\n|\n$/g, '');

Note this removes all whitespace and not just \n.

Template literals

See Template literals on Mozilla docs.

Split

Split by delimeter

'abc def ghi'.split(' ')
// [ 'abc', 'def', 'ghi' ]

String to array of characters

'abcdef'.split('')
// [ 'a', 'b', 'c', 'd', 'e', 'f' ]