revision:
The search() method matches a string against a regular expression and returns the index (position) of the first match. It returns -1 if no match is found. The search() method is case sensitive.
If the search value is a string, it is converted to a regular expression.
string.search(searchValue)
Parameters:
searchvalue : required. The search value. A regular expression (or a string that will be converted to a regular expression).
<p>search() searches a string for a value and returns the position of the first match:</p>
<p id="demo"></p>
<script>
let text = "Mr. Blue has a blue house"
let position = text.search("Blue");
document.getElementById("demo").innerHTML = position;
</script>
<div>
<p id="search-1"></p>
<p id="search-2"></p>
<p id="search-3"></p>
<p id="search-4"></p>
<p id="search-5"></p>
<p id="search-6"></p>
</div>
<script>
let text = "Mr. Blue has a blue house"
document.getElementById("search-1").innerHTML = "sentence : " + text;
let position = text.search("Blue");
document.getElementById("search-2").innerHTML = "position 'Blue' : " + position;
let position2 = text.search("blue");
document.getElementById("search-3").innerHTML = "position 'blue' : " + position2;
let position3 = text.search(/Blue/);
document.getElementById("search-4").innerHTML = "position '/Blue/' : " + position3;
let position4 = text.search(/blue/);
document.getElementById("search-5").innerHTML = "position '/blue/' : " + position4;
let position5= text.search(/blue/i);
document.getElementById("search-6").innerHTML = "position '/blue/i' : " + position5;
</script>