没有参数无法解析自定义手把助手

Question

I am creating a handlebars helper, which takes the following form:

define(['Handlebars'], function (Handlebars) {
    Handlebars.registerHelper("myHelper", function (options) {
        console.log('myHelper');
        if (*condition*) {
            console.log('myHelper False');
            return options.inverse(this);
        } else {
            console.log('myHelper True');
            return options.fn(this);
        }
    });
});

As you can see, I'm using require.js. I'm also using this as part of a Backbone.js application. In the template, the helper is called like so:

{{#myHelper}}
<!-- Some HTML -->
{{else}}
<!-- Some HTML -->
{{/myHelper}}

However, the helper always returns false because it is not recognized. I know this because the console.log is never called. I have other custom helpers in the application that work, but they all take in arguments. If I add a dummy argument, the helper works fine:

define(['Handlebars'], function (Handlebars) {
    Handlebars.registerHelper("myHelper", function (dummy, options) {
        console.log('myHelper');
        if (*condition*) {
            console.log('myHelper False');
            return options.inverse(this);
        } else {
            console.log('myHelper True');
            return options.fn(this);
        }
    });
});

Template:

{{#myHelper "string"}}
<!-- Some HTML -->
{{else}}
<!-- Some HTML -->
{{/myHelper}}

I'm using handlebars v1.0.0. Is this something that is addressed in 2.0.0? This isn't blocker, but I clearly would prefer not to use a dummy argument if possible.

Answer 1

Here is fiddle with helper you need. handlebars-1.0.rc.1 used. Also tried with handlebars-1.3.0 - works fine.

HTML

<script id="topLevel" type="text/x-handlebars-template">
    {{#myHelper}}
        it's truthy
    {{else}}
        it's falsy
    {{/myHelper}}
</script>

JS

Handlebars.registerHelper('myHelper', function (options) {
    if (true) {
        console.log("It's true");
        return options.fn(this);
    }
    console.log("It's false");
    return options.inverse(this);
});

var _template =  Handlebars.compile($('#topLevel').html());
$('body').append(_template());

So your issue could occur:

Outdated library or you are trying to use helper before it has been registered. Require.js loads libraries/files asynchronously, call handlebars as dependency. Example:

define(function(require){
    var yourObj = function() {
      require(['handlebars'], function (Handlebars) {
      // use Handlebars here
      });
    };
    return yourObj;
}); 

Hope it's help.