no-loop-func
禁止在循环语句中包含不安全引用的函数声明
由于函数在循环周围创建闭包的方式，在循环中编写函数往往会导致错误。例如：
¥Writing functions within loops tends to result in errors due to the way the function creates a closure around the loop. For example:
for (var i = 0; i < 10; i++) {
funcs[i] = function() {
return i;
};
}
在这种情况下，你会期望在循环中创建的每个函数都返回不同的数字。实际上，每个函数都返回 10，因为这是作用域中 i 的最后一个值。
¥In this case, you would expect each function created within the loop to return a different number. In reality, each function returns 10, because that was the last value of i in the scope.
let 或 const 缓解了这个问题。
¥let or const mitigate this problem.
for (let i = 0; i < 10; i++) {
funcs[i] = function() {
return i;
};
}
在这种情况下，循环中创建的每个函数都按预期返回不同的数字。
¥In this case, each function created within the loop returns a different number as expected.
规则详情
¥Rule Details
引发此错误是为了高亮一段可能无法按预期工作的代码，并且还可能表明对该语言的工作方式存在误解。如果你不修复此错误，你的代码可能会毫无问题地运行，但在某些情况下，它可能会出现意外行为。
¥This error is raised to highlight a piece of code that may not work as you expect it to and could also indicate a misunderstanding of how the language works. Your code may run without any problems if you do not fix this error, but in some situations it could behave unexpectedly.
此规则不允许循环中包含不安全引用的任何函数（例如，从外部范围修改变量）。此规则忽略 IIFE，但不忽略异步或生成器函数。
¥This rule disallows any function within a loop that contains unsafe references (e.g. to modified variables from the outer scope). This rule ignores IIFEs but not async or generator functions.
此规则的错误代码示例：
¥Examples of incorrect code for this rule:
/*eslint no-loop-func: "error"*/
var i = 0;
while(i < 5) {
var a = function() { return i; };
a();
i++;
}
var i = 0;
do {
function a() { return i; };
a();
i++
} while (i < 5);
let foo = 0;
for (let i = 0; i < 10; ++i) {
//Bad, `foo` is not in the loop-block's scope and `foo` is modified in/after the loop
setTimeout(() => console.log(foo));
foo += 1;
}
for (let i = 0; i < 10; ++i) {
//Bad, `foo` is not in the loop-block's scope and `foo` is modified in/after the loop
setTimeout(() => console.log(foo));
}
foo = 100;
var arr = [];
for (var i = 0; i < 5; i++) {
arr.push((f => f)(() => i));
}
for (var i = 0; i < 5; i++) {
arr.push((() => {
return () => i;
})());
}
for (var i = 0; i < 5; i++) {
(function fun () {
if (arr.includes(fun)) return i;
else arr.push(fun);
})();
}
此规则的正确代码示例：
¥Examples of correct code for this rule:
/*eslint no-loop-func: "error"*/
var a = function() {};
for (var i=10; i; i--) {
a();
}
for (var i=10; i; i--) {
var a = function() {}; // OK, no references to variables in the outer scopes.
a();
}
for (let i=10; i; i--) {
var a = function() { return i; }; // OK, all references are referring to block scoped variables in the loop.
a();
}
var foo = 100;
for (let i=10; i; i--) {
var a = function() { return foo; }; // OK, all references are referring to never modified variables.
a();
}
//... no modifications of foo after this loop ...
var arr = [];
for (var i=10; i; i--) {
(function() { return i; })();
}
for (var i = 0; i < 5; i++) {
arr.push((f => f)((() => i)()));
}
for (var i = 0; i < 5; i++) {
arr.push((() => {
return (() => i)();
})());
}
版本
此规则是在 ESLint v0.0.9 中引入。