add solution 008[js]

Author: limbowandering

solution/008. String to Integer (atoi)/Solution.js

@@ -0,0 +1,23 @@
+const myAtoi = function(str){
+  str = str.trim();
+  if(!str) return 0;
+  let isPositive = 1;
+  let i = 0, ans = 0;
+  if(str[i] === '+'){
+    isPositive = 1;
+    i++;
+  }else if(str[i] === '-'){
+    isPositive = 0;
+    i++;
+  }
+  for(; i < str.length; i++){
+    let t = str.charCodeAt(i) - 48;
+    if(t > 9 || t < 0) break;
+    if(ans > 2147483647/10 || ans > (2147483647-t)/10){
+      return isPositive ? 2147483647 : -2147483648;
+    }else{
+      ans = ans*10 + t;
+    }
+  }
+  return isPositive? ans : -ans;
+}