JSLint：意外的赋值表达式

由一脸苍白i发布于 2020-05-23 20:44:11

我收到此警告：

Unexpected assignment expression.
return task.completed = true; // Line 63, Pos 39

使用此代码时：

completeAll: function () {
    this.tasks = this.tasks.filter(function (task) {
        return task.completed = true;
    });
}

为什么？而且我还能如何编写该表达式以避免JSLint引发警告？

附言

The codeblock is taken from the Vue TodoMVC Example here: http://todomvc.dev/examples/vue/, therefore I assume that code review must have already been happened.

三叔公

2020-05-23 20:44:11

It's doing that because it's warning you that you're using = rather than == or === in a context where you're not just assigning, but also doing something with the assigned result. That's perfectly valid JavaScript, but it's frequently unintentional. A better example is:

if (foo = bar) {
    // ...
}

...where you probably meant == or === (checking that they were equal).

How you fix it depends on what you're trying to do. From the name of the method, I assume you're (well, they're) trying to set task.completed, in which case frankly filter is the wrong function to use; they should be using forEach:

completeAll: function () {
    this.tasks.forEach(function (task) {
        task.completed = true;
    });
}

but if you (they) really wanted to use filter:

completeAll: function () {
    this.tasks = this.tasks.filter(function (task) {
        task.completed = true;
        return true; // Or return task.completed
    });
}

如果您要进行比较（我对此表示怀疑），而不是进行分配，那么：

return task.completed == true;

要么

return !!task.completed;

要么

return task.completed; // If you know it's boolean already

一脸苍白i

这家伙很懒，什么都没留下

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