+ 1

J.S. What exactly does 'indexOf' and LastIndexOf' do?

var str = "Please locate where 'locate' occurs!"; var pos = str.indexOf("locate");

12th Jun 2019, 4:20 AM
Ginfio
Ginfio - avatar
4 Respostas
+ 12
1. string.indexOf(substr, pos); It looks for the substr in string, starting from the given position pos, and returns the position where the match was found or -1 if nothing can be found. For example: let string = "Sololearn"; console.log(string.indexOf("Solo")); // 0, coz "Solo" was found at the begining console.log(string.indexOf("solo")); // -1, not found, coz search is case-sensitive The optional second parameter allows us to search starting from the given position For example (let's find second occurrence of "ol"): let string = "Sololearn"; console.log(string.indexOf("ol", 2)); // 3 You can find all occurrences with help of loop and this amazing method (will be task for you). 2. string.lastIndexOf(substr, pos); This is a similar method that searches from the end of a string to its begining. It would list the occurrence in the reverse order. For example: let string = "Sololearn"; console.log(string.lastIndexOf("ol")); // 3 You can read more about this methods on MDN: https://developer.mozilla.org
12th Jun 2019, 5:47 AM
Вап
+ 2
Better try it on code playground, and tell us the output.
12th Jun 2019, 5:00 AM
Calviղ
Calviղ - avatar
+ 1
Index number 7 for the word staring pos of word "locate" . Count from index 0, the first letter from the left. P l e a s e locate... 0 1 2 3 4 5 6 7
12th Jun 2019, 5:39 AM
Calviղ
Calviղ - avatar
0
output = 7 I got it from w3school and it just didn't make sense: https://www.w3schools.com/js/tryit.asp?filename=tryjs_string_indexof
12th Jun 2019, 5:03 AM
Ginfio
Ginfio - avatar