为什么在 JavaScript 中打印 12 而不是 10 [关闭]

Question

每次尝试此操作时，控制台日志都会打印 12 而不是 10：

let number1 = 3;
let number2 = 2;
number1 += number2;
number2 += number1;
let result = number1 + number2;
console.log(result);

Answer 1

let number1 = 3; 
let number2 = 2; 

number1 += number2;
// number1 = 3 + 2 = 5; 

number2 += number1;
// number2 = 2 + 5 = 7; 

let result = number1 + number2;
// result = 5 + 7 = 12;
 
console.log(result);

为什么结果应该是10？