https://leetcode.com/problems/string-to-integer-atoi/

myAtoi.js

var myAtoi = function(str) {
    
    str = str.trim();
    if(!str.length) return 0;
    let negative = false;
    
    const chars = [];
    if(!str[0].match(/[0-9\+\-]/)) return 0;
    
    let i = 0;
    if(str[0] === '-'){
        negative = true;
        i++;
    }
    else if(str[0] === '+') i++;
    
    for(null; i<str.length; i++){
        if(str[i].match(/[0-9]/)) chars.push(str[i]);
        else break;
    }
    
    if(!chars.length) return 0;
    
    const numStr = chars.join('');
    const num = parseInt(numStr); // because I can't stomach doing even more work
    
    const maxInt = (1<<30)-1 + (1<<30);
    
    if(num > maxInt) return negative ? (-maxInt-1) : maxInt;
    
    if(negative) return -num;
    return num;
};