Handlebars.js Else If | 易学教程

问题

I'm using Handlebars.js for client side view rendering. If Else works great but I've encountered a 3 way conditional that requires ELSE IF:

This doesn't work:

{{#if FriendStatus.IsFriend }}
    <div class="ui-state-default ui-corner-all" title=".ui-icon-mail-closed"><span class="ui-icon ui-icon-mail-closed"></span></div>
{{else if FriendStatus.FriendRequested}}
    <div class="ui-state-default ui-corner-all" title=".ui-icon-check"><span class="ui-icon ui-icon-check"></span></div>
{{else}}
    <div class="ui-state-default ui-corner-all" title=".ui-icon-plusthick"><span class="ui-icon ui-icon-plusthick"></span></div>
{{/if}}

How do I do ELSE IF with handlebars?

回答1:

Handlebars supports {{else if}} blocks as of 3.0.0.

Handlebars v3.0.0 or greater:

{{#if FriendStatus.IsFriend}}
  <div class="ui-state-default ui-corner-all" title=".ui-icon-mail-closed"><span class="ui-icon ui-icon-mail-closed"></span></div>
{{else if FriendStatus.FriendRequested}}
  <div class="ui-state-default ui-corner-all" title=".ui-icon-check"><span class="ui-icon ui-icon-check"></span></div>
{{else}}
  <div class="ui-state-default ui-corner-all" title=".ui-icon-plusthick"><span class="ui-icon ui-icon-plusthick"></span></div>
{{/if}}

Prior to Handlebars v3.0.0, however, you will have to either define a helper that handles the branching logic or nest if statements manually:

{{#if FriendStatus.IsFriend}}
  <div class="ui-state-default ui-corner-all" title=".ui-icon-mail-closed"><span class="ui-icon ui-icon-mail-closed"></span></div>
{{else}}
  {{#if FriendStatus.FriendRequested}}
    <div class="ui-state-default ui-corner-all" title=".ui-icon-check"><span class="ui-icon ui-icon-check"></span></div>
  {{else}}
    <div class="ui-state-default ui-corner-all" title=".ui-icon-plusthick"><span class="ui-icon ui-icon-plusthick"></span></div>
  {{/if}}
{{/if}}

回答2:

I usually use this form:

{{#if FriendStatus.IsFriend}}
  ...
{{else}} {{#if FriendStatus.FriendRequested}}
  ...
{{else}}
  ...
{{/if}}{{/if}}

回答3:

The spirit of handlebars is that it is "logicless". Sometimes this makes us feel like we are fighting with it, and sometimes we end up with ugly nested if/else logic. You could write a helper; many people augment handlebars with a "better" conditional operator or believe that it should be part of the core. I think, though, that instead of this,

{{#if FriendStatus.IsFriend}}
  <div class="ui-state-default ui-corner-all" title=".ui-icon-mail-closed"><span class="ui-icon ui-icon-mail-closed"></span></div>
{{else}}
  {{#if FriendStatus.FriendRequested}}
    <div class="ui-state-default ui-corner-all" title=".ui-icon-check"><span class="ui-icon ui-icon-check"></span></div>
  {{else}}
    <div class="ui-state-default ui-corner-all" title=".ui-icon-plusthick"><span class="ui-icon ui-icon-plusthick"></span></div>
  {{/if}}
{{/if}}

you might want to arrange things in your model so that you can have this,

{{#if is_friend }}
  <div class="ui-state-default ui-corner-all" title=".ui-icon-mail-closed"><span class="ui-icon ui-icon-mail-closed"></span></div>
{{/if}}

{{#if is_not_friend_yet }}
    <div class="ui-state-default ui-corner-all" title=".ui-icon-check"><span class="ui-icon ui-icon-check"></span></div>
{{/if}}

{{#if will_never_be_my_friend }}
    <div class="ui-state-default ui-corner-all" title=".ui-icon-plusthick"><span class="ui-icon ui-icon-plusthick"></span></div>
{{/if}}

Just make sure that only one of these flags is ever true. Chances are, if you are using this if/elsif/else in your view, you are probably using it somewhere else too, so these variables might not end up being superfluous.

Keep it lean.

回答4:

Handlebars now supports {{else if}} as of 3.0.0. Therefore, your code should now work.

You can see an example under "conditionals" (slightly revised here with an added {{else}}:

    {{#if isActive}}
      <img src="star.gif" alt="Active">
    {{else if isInactive}}
      <img src="cry.gif" alt="Inactive">
    {{else}}
      <img src="default.gif" alt="default">
    {{/if}}

http://handlebarsjs.com/block_helpers.html

回答5:

I wrote this simple helper:

Handlebars.registerHelper('conditions', function (options) {
    var data = this;
    data.__check_conditions = true;
    return options.fn(this);
});


Handlebars.registerHelper('next', function(conditional, options) {
  if(conditional && this.__check_conditions) {
      this.__check_conditions = false;
      return options.fn(this);
  } else {
      return options.inverse(this);
  }
});

It's something like Chain Of Responsibility pattern in Handlebars

Example:

    {{#conditions}}
        {{#next condition1}}
            Hello 1!!!
        {{/next}}
        {{#next condition2}}
            Hello 2!!!
        {{/next}}
        {{#next condition3}}
            Hello 3!!!
        {{/next}}
        {{#next condition4}}
            Hello 4!!!
        {{/next}}
    {{/conditions}}

It's not a else if but in some cases it may help you)

来源：https://stackoverflow.com/questions/10736907/handlebars-js-else-if

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handlebars.js