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String: indexOf()

To determine the first occurrence of a string within another string, use the indexOf method:
var n1 = 'bit'.indexOf('it');
var n2 = 'bit'.indexOf('js');
var n3 = 'bit'.indexOf('IT');
n1 is 1, because the starting position of 'it' in 'bit' is 1. As usual, counting starts at 0. indexOf returns -1 if the search string does not occur in the calling string. Thus n2 is -1. The indexOf method is case sensitive. So n3 is also -1.

Exercise

Write a function indexOfIgnoreCase taking two strings and determining the first occurrence of the second string in the first string. The function should be case insensitive. indexOfIgnoreCase('bit','it') and indexOfIgnoreCase('bit','IT') should return 1.
var indexOfIgnoreCase = function(s1, s2) {
// Change s1 and s2
// first to lowercase.
// Then use the
// indexOf method. 
};
var indexOfIgnoreCase = function(s1, s2) {
  var s1Lower = s1.toLowerCase();
  var s2Lower = s2.toLowerCase();
  return s1Lower.indexOf(s2Lower);
};