Monthly Archives: August 2018

Mustache templating for displaying data (JS)

ref –

Templates are a great way to separate your website’s code from its design.

Mustache is a logic-less template syntax. It can be used for HTML, config files, source code – anything.

It works by expanding tags in a template using values provided in a hash or object

One of Mustache’s big plus points is that is logic-less, which means it keeps your templates very neat and tidy. There are no messy if … then or looping constructs embedded within a Mustache template; it’s all just markup and simple Mustache tags. All the logic is hidden away inside your data objects (and the code that creates or fetches them).

A mustache template is a string that contains any number of mustache tags.

Tags are indicated by the double mustaches that surround them.
{{person}} is a tag, as is {{#person}}

Using mustache basics

  • First, we’ll include mustache js file
  • Second, we’ll create a template with tags
  • Then, we’ll use a object’s values provided by its properties
  • Finally, we’ll see the output from the template + object by using Mustache.render

include the mustache js file in your header

Create the template

The template is a string.
For example: “{{name}} is a {{occupation}}

The tags are:

It expands the tags by using object view.
It looks inside this object for properties name and occupation. Then it would expand the tags with the values occupied at properties name, and occupation.

Load the template

Then, simply execute our tags, templates, objects, and render them.
Id person for paragraph p is to hold the result.

Another Example

This time, we introduce the concept of sections.

Sections render blocks of text one or more times, depending on the value of the key in the current context. A section begins with a hashtag and ends with a slash:


The behavior of the section is determined by the value of the key:


Since the object property is true, we display what’s between Robot tags.

My name is Pinocchio!

Your output when you run the web file is:

Hello Pinocchio You live in the woods! Well, you are friends with animals

Inverted Sections

An inverted section begins with a caret (hat) and ends with a slash.

Inverted section means when its false, it displays. When true, it won’t display.



Since Robot is false, let’s display what’s in between the Robot tags because this is an inverted section.

No content!

Another Example

In this next example, we’ll first use textarea to hold strings that can represent our templates and data objects. You can specify the strings in your html code, or simply have the user enter them via the web page.

In html, you can put the contents of the textarea in between textarea tags. Thus, that is the text that will be appear when the textarea tags are rendered on the web page. In our case, we put the template string inside the textarea with id template.

When we’re processing the code, we need to get whatever the input is from the textarea “template”. Thus, we get the string from the textarea via javascript like so:

In, Mustache.Render(template, object), the template parameter needed is a string. Thus, our templateStr can simply be passed in.

The string we pass into the textarea “data” is the object. However, the object must be a code evaluation. In other words, we have to convert the string into code. We can use javascript’s eval function.

Remember that whatever variable you decide to use for the object in dataStr must be used in code.

In our case, it is “hadoken”.

In our js, we basically get the data from the textareas. Then pass them into Mustache.render function. It returns the result that we need.

And we finally throw that result into the html.


Source Code




selecting ranges with nth-child

Say we have a list.

We want to select all the list items and border it red.

We want to select all the odd

we want to seelct all the evens

We want to select ranges.



new (js)

ref –

Prototype and Inheritance in JS (non-class)

Creating a user-defined object requires two steps:

1) Define the object type by writing a function.

2) Create an instance of the object with new.

To define an object type, create a function for the object type that specifies its name and properties. An object can have a property that is itself or another object.

When the code new Foo(…) is executed, the following things happen:

1) A new object is created, inheriting from Foo.prototype.

2) The constructor function Foo is called with the specified arguments, and with this bound to the newly created object. new Foo is equivalent to new Foo(), i.e. if no argument list is specified, Foo is called without arguments.

3) Normally constructors don’t return a value.

If the constructor function doesn’t explicitly return an object, the object created in step 1 is used instead.
However, sometimes, they can choose to do so if they want to override the normal object creation process of using step 1.
If they do return an object in the constructor function, then the object returned by the constructor function becomes the result of the whole new expression. Reference p would then point to this returned object.

Built in Methods (js)

ref –

Use Object.assign to assign properties of objects over to your destination object.

Using Object.assign, if there already exist a property/value, and you assign a new property that has the same name over, then the existing property/value gets replaced.

Using Object.assign, we can also do a deep copy of an object.

find and findIndex both find elements for you. It is important to note that find() will return the FIRST element in the Array that satisfies the provided testing function.

Use find to see if ‘d’ exists.

find – looping: a
find – looping: b
find – looping: c
find – looping: c
find – looping: d
res: d

Use findIndex to see if ‘c’ exists.

findIndex – looping: a
findIndex – looping: b
findIndex – looping: c


The reason isNaN() is “broken” is because, ostensibly, type conversions aren’t supposed to happen when testing values.

That is the issue Number.isNaN() is designed to address.

In particular, Number.isNaN() will only attempt to compare a value to NaN if the value is a number-type value.

Any other type will return false, even if they are literally “not a number”, because the type of the value NaN is number.

You can also think of it as anything that’s not NaN when passed to Number.isNaN will return false, while passing NaN into it will yield true.

The ES5 global.isNaN method, in contrast, casts non-numeric values passed to it before evaluating them against NaN, using Number(…)

That produces significantly different results. The example below produces inconsistent results because, unlike Number.isNaN, isNaN casts the value passed to it through Number first.

Number.isNaN will return false immediately if the argument is not a Number

while isNaN first converts the value to a Number

For isNaN():

then it does a NaN === NaN comparison, which results to true.

for Number.isNumber() , as mentioned earlier, we check to see the type of the argument is a Number. If its not a Number, it returns false immediately!

Infinity is actually NOT infinity, it a numeric value that represents Infinity. The actual value is 1.797693134862315E+308. The same for -Infinity, -1.797693134862315E+308

static and non-static (js)

ref –

Static methods, like many other features introduced in ES6, are meant to provide class-specific methods for object-oriented programming in Javascript.

Static methods are often used to create utility functions for an application.

Static methods are called without instantiating their class…

thus, when we call static “triple”, you will won’t see the log in the constructor executed.

Static methods…are also not callable when the class is instantiated.

Since these methods operate on the class instead of instances of the class, they are called on the class.

Say we have a subclass to a parent class, any static methods that we declared are available to the subclasses as well