题目：

Implement a function that adds two numbers together and returns their sum in binary. The conversion can be done before, or after the addition.

The binary number returned should be a string.

答案：

// 1
function addBinary (a, b) {
　　return (a + b).toString(2);
}

// 2
function addBinary (a, b) {
　　return ((a + b) >>> 0).toString(2);
}

// 3
const addBinary = (a, b) => (a + b).toString(2);

7kyu Binary Addition