string to integer (atoi) javascript
/**
* @param {string} str
* @return {number}
*/
var myAtoi = function(str) {
var i = 0;
var sign = 1;
var res = 0;
var len = str.length;
var INT_MAX = 2147483647;
var INT_MIN = - INT_MAX - 1;
while (str[i] === ' ') i++;
if (str[i] === '+' || str[i] === '-') {
sign = str[i] === '+' ? 1 : -1;
i++;
}
while (str[i] >= '0' && str[i] <= '9') {
res = (res * 10) + (str[i] - 0);
if (sign === 1 && res > INT_MAX) return INT_MAX;
if (sign === -1 && res > INT_MAX + 1) return INT_MIN;
i++;
}
return res * sign;
};