How to implement advanced JEXL functions in Peaka

Unary Operators

Example

The exclamation mark negates the boolean that appears next to it.

    {{!true}}

Binary Operators

Comparisons

A note about in

The in operator can be used to check for a substring: "Cad" in "Ron Cadillac", and it can be used to check for an array element: "coarse" in ['fine', 'medium', 'coarse']. However, the == operator is used behind-the-scenes to search arrays, so it should not be used with arrays of objects. The following expression returns false: {a: 'b'} in [{a: 'b'}].

Ternary operator

Conditional expressions are used to check if the first segment returns a correct value. If that’s the case, the value in the next segment is applied. Otherwise, the other value is applied. If the next segmeent is missing, the test result itself will be used instead.

Native Types

Groups

Parentheses work just how you'd expect them to:

Identifiers

Access variables in the context object by just typing their name. Objects can be accessed with dot notation, or by using brackets to access a dynamic property name.

Example context:

{
  name: {
    first: "Malory",
    last: "Archer"
  },
  exes: [
    "Nikolai Jakov",
    "Len Trexler",
    "Burt Reynolds"
  ],
  lastEx: 2
}

Functions

In JEXL, common built-in functions are readily available, but also functions library is extended with lodash functions.

You can use lodash functions from this link.

Additionally, you can check our functions from this article.

Example

Check out the JEXL codes below:

Find Min

    {{ min([65, 42, 87, 88]) }}

    // => 42

Reverse Array

    {{ reverse([1, 2, 3, 4]) }}

    // => [4, 3, 2, 1]

Check Equal

    {{ eq({ a:1 }, { a:1 }) }}
    // => true

    {{ eq(3, 4) }}
    // => false

Add Elements To Array

    {{ concat([1], 2, 3, 4) }}

    // => [1, 2, 3, 4]

Get Last Element of Array

    {{ reverse([1, 2, 3]) }}

    // => 3