Occurence and position of a substring in a string
Description :
In Javascript we can use the indexOf method to find the FIRST occurence(starting index)
of a string in another string.
The lastIndexOf method can be used to find the LAST occurence(starting index) of a string
in another string.
You can also specify which index to start searching from as a second parameter.
Note that JS starts counting from 0. If there are no results -1 is returned.
Syntax :
let changed_string = original_string.indexOf(query_string);
let changed_string = original_string.indexOf(query_string, index_to_start);
let changed_string = original_string.lastIndexOf(query_string);
Examples :
let firstWord = "tree";
let sentence = "A tree";
let position = sentence.indexOf(firstWord);
position = ??
let firstWord = "apple";
let sentence = "apple apple is not apple";
let position = sentence.lastIndexOf(firstWord);
let secondPosition = sentence.indexOf(firstWord, 5);
position = ??
secondPosition = ??
let firstWord = "no";
let sentence = "yes is a valid response";
let firstPosition = sentence.indexOf(firstWord);
let lastPosition = sentence.lastIndexOf(firstWord);
position = ??
lastPosition = ??