Javascript 为什么 setInterval 回调只执行一次？
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Why does the setInterval callback execute only once?
提问by computer_smile
I have this counter I made but I want it to run forever, it's really simple, what am I doing wrong here?
我有我制作的这个计数器，但我希望它永远运行，这真的很简单，我在这里做错了什么？
function timer() {
console.log("timer!")
}
window.setInterval(timer(), 1000)
回答by Koen Peters
You used a function call instead of a function reference as the first parameter of the setInterval. Do it like this:
您使用函数调用而不是函数引用作为 setInterval 的第一个参数。像这样做：
function timer() {
console.log("timer!");
}
window.setInterval(timer, 1000);
Or shorter (but when the function gets bigger also less readable):
或者更短（但当函数变大时，可读性也会降低）：
window.setInterval( function() {
console.log("timer!");
}, 1000)
回答by Bakudan
setIntervaland setTimeoutmustbe used with callbacks, like:
setInterval并且setTimeout必须与回调一起使用，例如：
setInterval(timer, 1000);
or unnamed functions:
或未命名的函数：
setInterval( function() { console.log("timer!"); }, 1000 );
Why your code is not working - when you pass a function as argument to another function with brackets e.g. doSomething ( someFunc() )you are passing the result of the function.
为什么您的代码不起作用 - 当您将一个函数作为参数传递给另一个带括号的函数时，例如doSomething ( someFunc() )您正在传递函数的结果。
When the function is passed as object e.g. doSomething ( someFunc )you are passing a callback. This way someFuncis passed as reference and it is executed somewhere in the calling function. This is the same as the pointers to functions in other languages.
当函数作为对象传递时，例如doSomething ( someFunc )您正在传递回调。这种方式someFunc作为引用传递，并在调用函数的某处执行。这与其他语言中的函数指针相同。
A common mistake is to use the these two functions as shown at w3schools. This makes an implicit call to eval.
一个常见的错误是使用w3schools 中显示的这两个函数。这对 进行了隐式调用eval。
