no-useless-call
禁止对 .call() 和 .apply() 进行不必要的调用
函数调用可以由 Function.prototype.call() 和 Function.prototype.apply() 编写。但是 Function.prototype.call() 和 Function.prototype.apply() 比正常的函数调用要慢。
¥The function invocation can be written by Function.prototype.call() and Function.prototype.apply().
But Function.prototype.call() and Function.prototype.apply() are slower than the normal function invocation.
规则详情
¥Rule Details
此规则旨在标记 Function.prototype.call() 和 Function.prototype.apply() 的使用情况，可以用正常的函数调用替换。
¥This rule is aimed to flag usage of Function.prototype.call() and Function.prototype.apply() that can be replaced with the normal function invocation.
此规则的错误代码示例：
¥Examples of incorrect code for this rule:
/*eslint no-useless-call: "error"*/
// These are same as `foo(1, 2, 3);`
foo.call(undefined, 1, 2, 3);
foo.apply(undefined, [1, 2, 3]);
foo.call(null, 1, 2, 3);
foo.apply(null, [1, 2, 3]);
// These are same as `obj.foo(1, 2, 3);`
obj.foo.call(obj, 1, 2, 3);
obj.foo.apply(obj, [1, 2, 3]);
此规则的正确代码示例：
¥Examples of correct code for this rule:
/*eslint no-useless-call: "error"*/
// The `this` binding is different.
foo.call(obj, 1, 2, 3);
foo.apply(obj, [1, 2, 3]);
obj.foo.call(null, 1, 2, 3);
obj.foo.apply(null, [1, 2, 3]);
obj.foo.call(otherObj, 1, 2, 3);
obj.foo.apply(otherObj, [1, 2, 3]);
// The argument list is variadic.
// Those are warned by the `prefer-spread` rule.
foo.apply(undefined, args);
foo.apply(null, args);
obj.foo.apply(obj, args);
已知限制
¥Known Limitations
此规则静态比较代码以检查 thisArg 是否更改。所以如果关于 thisArg 的代码是动态表达式，这条规则就不能正确判断。
¥This rule compares code statically to check whether or not thisArg is changed.
So if the code about thisArg is a dynamic expression, this rule cannot judge correctly.
此规则的错误代码示例：
¥Examples of incorrect code for this rule:
/*eslint no-useless-call: "error"*/
a[i++].foo.call(a[i++], 1, 2, 3);
此规则的正确代码示例：
¥Examples of correct code for this rule:
/*eslint no-useless-call: "error"*/
a[++i].foo.call(a[i], 1, 2, 3);
何时不使用
¥When Not To Use It
如果你不想收到有关不必要的 .call() 和 .apply() 的通知，你可以放心地禁用此规则。
¥If you don’t want to be notified about unnecessary .call() and .apply(), you can safely disable this rule.
相关规则
版本
此规则是在 ESLint v1.0.0-rc-1 中引入。