How to remove characters from the end of a string with 'substr'?

Question

PHP

text text text 'what you need' text text
You also need to take into account what is required, it will constantly change, i.e. there will be a different number of characters.

Answer 1

Find the position of 'what you need'.
Find the length of 'what you need'.
Cut out 'what you want' with substr.

Answer 2

function rtrim( src, core) {
  var pos = src.indexOf(core);
  if( !!~pos) return src.substr(0, pos + core.length);
  else return src;
}

rtrim( "текст текст текст 'то что нужно' текст текст", "то что нужно") // текст текст текст 'то что нужно

Answer 3

I don't know why substr is here.

var t = 'текст текст текст то что нужно  213 213 12 321текст текст';
console.log(new RegExp('то что нужно', 'ig').exec(t)[0]);

Well, or replace everything that is not needed with an empty string.