Handlebarsjs check if a string is equal to a value

Question

Is it possible in Handlebars to check if a string is equal to another value without registering a helper? I can\'t seem to find anything relevant to this in the Handlebars r

Answer 1

It seems you can't do it "directly"

Try use helper, why not?

Register helper in your javascript code:

Handlebars.registerHelper('ifEquals', function(arg1, arg2, options) {
    return (arg1 == arg2) ? options.fn(this) : options.inverse(this);
});

Use in template:

{{#ifEquals sampleString "This is a string"}}
    Your HTML here
{{/ifEquals}}

More details here: Logical operator in a handlebars.js {{#if}} conditional

Update: Another way:

lets assume, your data is:

var data = {
    sampleString: 'This is a string'
};

Then (using jQuery):

$.extend(data, {isSampleString: function() {
    return this.sampleString ==  'This is a string';}
});

An use template:

{{#if isSampleString}}
    Your HTML here
{{/if}}

Answer 2

Use handlebars-helpers, which provides eq helper

Answer 3

The Mandrill mail service supports Handlebars and here it is possible to use "backticks" to evaluate an logical expression in a #if block:

{{#if `operating_system == "OS X"`}}
  <p>Click here for instructions to install on a Mac</p>
{{elseif `operating_system == "Windows"`}}
  <p>Click here for instructions to install on a PC</p>
{{/if}}

I don't know if this possible in general, but you should try it out. It works fine for me.

Answer 4

I would just use helpers like this:

Handlebars.registerHelper('ifeq', function (a, b, options) {
    if (a == b) { return options.fn(this); }
    return options.inverse(this);
});

Handlebars.registerHelper('ifnoteq', function (a, b, options) {
    if (a != b) { return options.fn(this); }
    return options.inverse(this);
});

Then in your code:

{{#ifeq variable "string"}} 
    ... do this ... 
{{/ifeq}}
{{#ifnoteq variable "string"}} 
    ... do this ... 
{{/ifnoteq}}

Answer 5

Node.js add this in server.js

const isEqual = function(a, b, opts) {
  if (a == b) {
    return opts.fn(this) 
  } else { 
    return opts.inverse(this) 
  } 
}

var hbs = require('hbs');
hbs.registerHelper('if_eq', isEqual);

Answer 6

A common case for a simple, re-usable helper function is to cause a return of string1 if values are equal and string2 if they are not.

Example:

Helper (let's call it "ifEqual" and send 4 parameters):

helpers: {

    ifEqual: function (obj, value, trueString, falseString) {
            return ( (obj===value) ? trueString : falseString );
}

Template Use:

For this example, assume the template receives a "transaction" object with a "transactionType" property: { transactionType: "expense", description: "Copies" }

Let's say our template has a <select> for the Transaction Type, with various <option>s as shown. We want to use Handlebars to pre-select the option which coincides with the value of transactionType.

Our new {{ ifEqual }} helper is used to insert "selected" for the <option> with the matching value of "expense."

<select required id="selTransactionType" name="selTransactionType" class="form-control" onchange='transactionTypeChanged()'>
   <option value='hourly' {{ ifEqual transaction.transactionType "hourly" "selected" "" }} >Hourly fee</option>
   <option value='flat' {{ ifEqual transaction.transactionType "flat" "selected" "" }} >Flat fee</option>
   <option value='expense' {{ ifEqual transaction.transactionType "expense" "selected" "" }} >Expense</option>
   <option value='payment' {{ ifEqual transaction.transactionType "payment" "selected" "" }} >Payment</option>
   <option value='credit' {{ ifEqual transaction.transactionType "credit" "selected" "" }} >Credit</option>
   <option value='debit' {{ ifEqual transaction.transactionType "debit" "selected" "" }} >Debit</option>
</select>