How to get index of letter in a string from end to begin?

Question

I can check that a string includes letter with using of .indexOf():

my_string = 'sdf sdfdsf dfdsdfs';
console.log(my_string.indexOf(' '));
// returns 4

Is exists method to do the same but from end to begin? (example above must returns 11 - the first white space from right to left)

`console.log(my_string.indexOf(' '));` returns 3 with your input, not 4. I don't know how you're expecting "11"; the first white space from right to left is in the 9th position? — Matt, Oct 27 '14 at 12:43
@user3775292, First white space from right to left is the 11th position from l to r and is index 10 from l to r — The One and Only ChemistryBlob, Oct 27 '14 at 12:45
If you're expecting 11 (actually, 10) then you're counting from left to right, not right to left as you state. Therefore the answers featuring `lastIndexOf()` will work for you. If you *don't* mean that, then @Savv's answer will work. — Ben, Oct 27 '14 at 12:45

score 2 · Answer 1 · answered Oct 27 '14 at 12:39

2

Reverse your string and perform indexOf():

reverseString = my_string.split("").reverse().join("");
console.log(my_string.length - reverseString.indexOf(' '));

answered Oct 27 '14 at 12:39

Savv

score 2 · Accepted Answer · answered Oct 27 '14 at 12:40

2

Use lastIndexOf.

my_string = 'sdf sdfdsf dfdsdfs';
console.log(my_string.lastIndexOf(' '));

answered Oct 27 '14 at 12:40

Scimonster

Why the best answer in http://stackoverflow.com/questions/18893402/javascript-indexof-from-end-of-search-string is define new method if lastIndexOf is exists? – AlexAstanin Oct 27 '14 at 12:57
That's a different usage, there they want to get the index of the end of the search, as opposed to the beginning. – Scimonster Oct 27 '14 at 12:59
Thanks for help, Scimonster. – AlexAstanin Oct 27 '14 at 13:00

score 0 · Answer 3 · answered Oct 27 '14 at 12:40

0

You can try this

console.log(my_string.lastIndexOf(" "));

answered Oct 27 '14 at 12:40

sp_m

3 Answers3