remove last 3 characters from string javascript

var str = "Hello";
var newString = str.substring(0, str.length - 1); //newString = Hellstr = str.slice(0, -3);let str = "12345.00";
str = str.slice(0, -1); 
console.log(str);let str = "12345.00";
str = str.substring(0, str.length - 1);
console.log(str);