CoffeeScript 总是以匿名函数返回 [英] CoffeeScript always returns in anonymous function

问题描述

I'm trying to write some CoffeScript function which checks all checkboxes in a table upon checking the checkbox in the th.

My function in CoffeeScript looks like this:

$("table.tableview th input:checkbox").live 'click', -> 
  checkedStatus = this.checked
  $("table.tableview tbody tr td:first-child input:checkbox").each ->
      this.checked = checkedStatus

It works great for checking all the boxes. However when unchecking it doesn't work. The compiled JS looks like this:

$("table.tableview th input:checkbox").live('click', function() {
  var checkedStatus;
  checkedStatus = this.checked;
  return $("table.tableview tbody tr td:first-child input:checkbox").each(function() {
    return this.checked = checkedStatus;
  });
});

It doesn't work because after the first one is set to false the return of the function will be false. I however have no clue how to suppress this default return behavior of coffee script. Please help.

When I add a "true" as per Flambino's suggestion I get the following JS

$("table.tableview th input:checkbox").live('click', function() {
    var checkedStatus;
    checkedStatus = this.checked;
    $("table.tableview tbody tr td:first-child input:checkbox").each(function() {
        return this.checked = checkedStatus;
    });
    return true;
});

The only way I can get the return statement inside the function is by putting it all the way like this:

$("table.tableview tbody tr td:first-child input:checkbox").each ->
    this.checked = checkedStatus
true

What am I doing wrong ? Thx for the help so far

解决方案

Just add a true as the last line of your function, and coffeescript will compile the JS to return that instead:

$("table.tableview th input:checkbox").live 'click', -> 
    checkedStatus = this.checked
    $("table.tableview tbody tr td:first-child input:checkbox").each ->
        this.checked = checkedStatus
    true

In other words, CoffeeScript always returns the result of the last line (like Ruby does)

---

Edit (after the question was updated):

Again, you can't keep CoffeeScript from returning the value of the last line in a function - part of the point of CoffeeScript is that it does exactly that.

CoffeeScript has significant whitespace, so indentation is what says what belongs together - your example is is actually correct:

$("table.tableview th input:checkbox").live 'click', -> 
    checkedStatus = this.checked
    $("table.tableview tbody tr td:first-child input:checkbox").each ->
        this.checked = checkedStatus
        true // cause this function (the each-iterator) to return true
    true // causes the click handler function to return true

There's no difference between this and just writing return true in a function like you would in javascript. You just use whitespace instead of {} to make code blocks.

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