> ## Documentation Index
> Fetch the complete documentation index at: https://docs.peaka.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How to implement advanced JEXL functions in Peaka

> Click here for an overview of the advanced functions in JEXL

### Unary Operators

| Operation | Symbol |
| --------- | :----: |
| Negate    |    !   |

**Example**

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

```
    {{!true}}
```

### Binary Operators

| Operation        | Symbol |
| ---------------- | :----: |
| Add, Concat      |    +   |
| Subtract         |    -   |
| Multiply         |   \*   |
| Divide           |    /   |
| Divide and floor |   //   |
| Modulus          |    %   |
| Power of         |    ^   |
| Logical AND      |   &&   |
| Logical OR       |  \|\|  |

### Comparisons

| Comparison                 | Symbol |
| -------------------------- | :----: |
| Equal                      |  `==`  |
| Not equal                  |  `!= ` |
| Greater than               |   `>`  |
| Greater than or equal      |  `>=`  |
| Less than                  |   `<`  |
| Less than or equal         |  `<=`  |
| Element in array or string |  `in`  |

**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.

| Expression                          | Result |
| ----------------------------------- | ------ |
| "" ? "Full" : "Empty"               | Empty  |
| "foo" in "foobar" ? "Yes" : "No"    | Yes    |
| `{agent: "Archer"}.agent ?: "Kane"` | Archer |

### Native Types

| Type     |           Examples           |
| -------- | :--------------------------: |
| Booleans |        `true`, `false`       |
| Strings  | "Hello "user"", 'Hey there!' |
| Numerics |     6, -7.2, 5, -3.14159     |
| Objects  |      `{hello: "world!"}`     |
| Arrays   |     \['hello', 'world!']     |

### Groups

Parentheses work just how you'd expect them to:

| Expression                   | Result |
| ---------------------------- | :----: |
| (83 + 1) / 2                 |   42   |
| 1 \< 3 && (4 > 2 \|\| 2 > 4) |  true  |

### 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:

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

| Expression         | Result        |
| ------------------ | ------------- |
| name.first         | Malory        |
| name\['la' + 'st'] | Archer        |
| exes\[2]           | Burt Reynolds |
| exes\[lastEx - 1]  | Len Trexler   |

### 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](https://lodash.com/docs/4.17.15).

Additionally, you can read [our documentation on JEXL](https://docs.peaka.com/jexl/built-in-functions/) to learn more about these functions.

**Example**

Check out the JEXL codes below:

*Find Min*

```java theme={null}
    {{ min([65, 42, 87, 88]) }}

    // => 42
```

*Reverse Array*

```java theme={null}
    {{ reverse([1, 2, 3, 4]) }}

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

*Check Equal*

```java theme={null}
    {{ eq({ a:1 }, { a:1 }) }}
    // => true

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

*Add Elements To Array*

```java theme={null}
    {{ concat([1], 2, 3, 4) }}

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

*Get Last Element of Array*

```java theme={null}
    {{ reverse([1, 2, 3]) }}

    // => 3
```