no-constant-condition
Disallow constant expressions in conditions
✅ Recommended
The "extends": "eslint:recommended" property in a configuration file enables this rule
作为测试条件的常量表达式（例如字面量）可能是一个错别字或开发触发的特定行为。例如，下面的代码看起来好像还没有准备好用于生产。
if (false) {
doSomethingUnfinished();
}
规则细节
这条规则不允许在以下测试条件中使用常量表达式：
if、for、while或do...while语句?:三元表达式
使用此规则的错误示例：
Open in Playground
/*eslint no-constant-condition: "error"*/
if (false) {
doSomethingUnfinished();
}
if (void x) {
doSomethingUnfinished();
}
if (x &&= false) {
doSomethingNever();
}
if (class {}) {
doSomethingAlways();
}
if (new Boolean(x)) {
doSomethingAlways();
}
if (Boolean(1)) {
doSomethingAlways();
}
if (undefined) {
doSomethingUnfinished();
}
if (x ||= true) {
doSomethingAlways();
}
for (;-2;) {
doSomethingForever();
}
while (typeof x) {
doSomethingForever();
}
do {
doSomethingForever();
} while (x = -1);
var result = 0 ? a : b;
if(input === "hello" || "bye"){
output(input);
}
使用此规则的正确示例：
Open in Playground
/*eslint no-constant-condition: "error"*/
if (x === 0) {
doSomething();
}
for (;;) {
doSomethingForever();
}
while (typeof x === "undefined") {
doSomething();
}
do {
doSomething();
} while (x);
var result = x !== 0 ? a : b;
if(input === "hello" || input === "bye"){
output(input);
}
选项
checkLoops
默认为 true。将此选项设置为 false 允许在循环中使用常量表达式。
当 checkLoops 为 false 时的正确示例：
Open in Playground
/*eslint no-constant-condition: ["error", { "checkLoops": false }]*/
while (true) {
doSomething();
if (condition()) {
break;
}
};
for (;true;) {
doSomething();
if (condition()) {
break;
}
};
do {
doSomething();
if (condition()) {
break;
}
} while (true)
Related Rules
Version
This rule was introduced in ESLint v0.4.1.