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Return the index of first character that appears twice in a string in JavaScript
We are required to write a JavaScript function that takes in a string and returns the index of first character that appears twice in the string.
If there is no such character then we should return -1.
Example
The code for this will be −
const str = 'Hello world, how are you';
const firstRepeating = str => {
const map = new Map();
for(let i = 0; i < str.length; i++){
if(map.has(str[i])){
return map.get(str[i]);
};
map.set(str[i], i);
};
return -1;
};
console.log(firstRepeating(str));Output
Following is the output on console −
2
Updated on: 10-Oct-2020
226 Views
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