The String search() method

Return the position of the first occurrence of the string passed as parameter in the current string.

It returns the index of the start of the occurrence, or -1 if no occurrence is found.

'JavaScript'.search('Script') //4
'JavaScript'.search('TypeScript') //-1

You can search using a regular expression (and in reality, even if you pass a string, that’s internally and transparently used as a regular expression too).

'JavaScript'.search(/Script/) //4
'JavaScript'.search(/script/i) //4
'JavaScript'.search(/a+v/) //1