i have an html block that contains few buttons and one text input. The placeholder of this text input should be changed in the different situations. 
Therefore i add a string variable. Then i put the html inside in another string variable: 

```
var dataType;

var htmlBlock = `<div class="icon negative big toleft" id="cancel-btn"><i class="fas fa-minus-circle"></i></div>
<div class="icon add big toleft"><i class="fas fa-check-circle"></i></div>
<input type="text" class="contact-input" style="margin-bottom: 5px;" maxlength="50" name="my-contact-phone" data-name="Name" placeholder=${dataType}>`

```

as you can see, in the last line of html code, i added ${dataType} in the placeholder part. 

then i use it with these codes:

```
if (document.getElementsByClassName('.js-phone'))
{
  dataType = "Add your number "
  this.html = this.phone.html();
  this.phone.html(
    htmlBlock
  )
};

```

after compiling, in the text input placeholder, this text appears: undefined 

Could anyone help me that how i can do it?
Your help will be appreciated.