What is the difference between slice() and substr() in JavaScript?

Question

Can I ask what the difference is between string object slice() and substr() in JavaScript?

Answer 1

var str="Hello world!";
document.write(str.substring(3,7)+"
");
document.write(str.slice(3,7)+"
");
document.write(str.substr(3,7));

result:

lo w
lo w
lo worl