String to integer (atoi)

stringToInteger.js

/**
 * @param {string} s
 * @return {number}
 */
var myAtoi = function(s) {
    let num = 0;
    let isNegative = false;
    let numString = "";
    let hasEncountered = false;
    let hasBeenPositive = false;
    for(let i=0; i<s.length; i++) {
        if(hasEncountered) {
            if(s[i].charCodeAt(0) < 48 || s[i].charCodeAt(0) > 57) break;
        }

        if(s[i].charCodeAt(0) < 32 || s[i].charCodeAt(0) > 57 || s[i].charCodeAt(0) == 46) break;

        if(!hasEncountered && s[i].charCodeAt(0) == 32) {
            if(hasBeenPositive || isNegative) break;
            continue;
        }
        if(!hasEncountered && s[i].charCodeAt(0) == 43) {
            if(isNegative || hasBeenPositive) break;
            hasBeenPositive = true;
            continue;
        }
        if(!hasEncountered && s[i].charCodeAt(0) == 45) {
            if(hasBeenPositive || isNegative) break;
            isNegative = true;
            continue;
        }

        if(s[i].charCodeAt(0) >= 48 && s[i].charCodeAt(0) <= 57) hasEncountered = true;
        numString += s[i];
    }

    if(numString.length != 0) {
        if(isNegative) num = numString * 1 * -1;
        else num = numString * 1;
    }

    if(num <= -2147483648) return -2147483648;
    if(num >= 2147483647) return 2147483647;
    
    return num;
};

// run a loop and for each character, check if any of the question rules have been broken
// if the character at the start (ignoring the whitespace) is negative then make the isNegative flag true
// if the character at the start (ignoring the whitespace) is positive then make the hasBeenPositive flag true 
// if at any time the number hasBeenPositive or Negative return 0
// else, if the number is negative return -num else return num

// Time: O(n)
// Space: O(1)