let a = document.querySelector('#b1').value;
console.log(`a: ${a}`);
document.querySelector('#b1').value = 10;
console.log(`a: ${a}`);
【问题讨论】：
a 是值的副本，它不会永久链接到输入。您需要重新分配变量。
let a = document.querySelector('#b1') 和 console.log(`a: ${a.value}`) 会给你正确的结果
标签： javascript dom
正如 cmets 中所说，
当您执行let a = document.querySelector('#b1').value; 时，它会解析该值并将其保存在变量a 中。
这样做，不会更新。要获得实际值，您需要每次都获得它。
像这样：
let wrongWay = document.getElementById("foo").value; // Getting it the wrong way
let rightWay = document.getElementById("foo"); // Getting it the right way
console.log("wrong way value : " + wrongWay);
console.log("right way value : " + rightWay.value);
// Changing input value
document.getElementById("foo").value = "new value";
console.log("Changed value !");
console.log("wrong way value : " + wrongWay); // The value isn't updated as it is saved as a string -> so it didn't get any update
console.log("right way value : " + rightWay.value); // By getting it, you are sure to get the right value<input id="foo" type="text" value="old value" >【讨论】：