/**
* @param {string} s
* @return {number}
*/
var myAtoi = function(s) {
let pre="",num="",idx=0
while(s[idx]===" "){
idx++;
}
while(s[idx]==="+"||s[idx]==="-"){
if(pre){
return 0;
}
pre=s[idx++];
}
while(s[idx]&&s[idx].charCodeAt()>=48&&s[idx].charCodeAt()<=57){
num+=s[idx++];
}
let res=Number(pre+num)||0;
res=Math.max((-2)**31,res);
res=Math.min(2**31-1,res);
return res
};