var a = "42";

​

var b = Number(a);

​

console.log(a);       // "42"

console.log(b);       // 42 -- the number!

​

// And here's an example of implicit coercion:

​

var a = "42";

​

var b = a * 1;  // "42" implicitly coerced to 42 here

​

console.log(a);       // "42"

console.log(b);       // 42 -- the number!