Question 218852 in Javascript Question posted in
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Javascript – how to get number from string without regex

Without using regex, is there a way to get number from a string in JavaScript?

For example, if input is "id is 12345", then I want 12345 number in output.

I know a lot of regex solutions, but I am looking for a non-regex tidy solution.

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2

Answers


  1. 0

    Iterate characters and parse each into a number. If the parsing is successful (check with isNaN()) then add it to the result number string. If the number sequence ends, break the loop:

    const str = 'id is 12345';

let num = '';

for(const char of str){
  if(!isNaN(parseInt(char))){
    num += char;
  }else if(num){
    break;
  }
}

console.log(+num);

    If you need to find all numbers you could use Array::reduce() since there’s no breaking loop or wasted looping to the end:

    const str = 'id is 12345 or 54321';

const nums = [...str, ''].reduce(({nums, num}, char) => {
  isNaN(parseInt(char)) ? num && nums.push(+num) && (num = '') : num +=char;
  return {nums, num};
}, {nums:[], num: ''}).nums;

console.log(nums);
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  2. 0

    You can loop over all the characters and build up numbers from consecutive digits.

    Here is one solution that works for multiple numbers (formed only using the characters 0-9).

    const str = "abc def 12345 xyz 987";
let res = [], curr = '';
for (const c of str + ' ') {
  if (c >= '0' && c <= '9') // add || c === '-' (to handle negatives)
    curr += c;
  else if (curr)
    res.push(+curr), curr = '';
    // use BigInt(curr) to handle larger numbers
}
console.log(res);
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