# Operators

An **operator** is a statement that evaluates some code, and makes a decision about what to do next. Operators can be used for comparing two values, inspecting a single value, or evaluating whether or not some code returns `true`.

{% hint style="info" %}
For further discussion on how Liquid treats values, see their documentation: [Truthiness and falsiness in Liquid](https://shopify.dev/docs/themes/liquid/reference/basics/true-and-false).
{% endhint %}

## Comparison operators

If `b = 6`, the table below illustrates the comparison operators and the way they interact with `b`:

| Operator | Description              | Example  | Result  |
| -------- | ------------------------ | -------- | ------- |
| `==`     | equal to                 | `b == 6` | `true`  |
| `!=`     | not equal                | `b != 6` | `false` |
| `>`      | greater than             | `b > 5`  | `true`  |
| `<`      | less than                | `b < 6`  | `false` |
| `>=`     | greater than or equal to | `b >= 6` | `true`  |
| `<=`     | less than or equal to    | `b <= 6` | `true`  |

### Examples

```liquid
{% assign order_qualifies = false %}

{% if order.cancelled_at == blank and cancel_risk %}
  {% assign order_qualifies = true %}
{% endif %}
```

```liquid
{% if has_product != true %}
  {% log "Order has no products; skipping" %}
  {% assign send_email = false %}
{% endif %}
```

### Testing for blank, empty

Liquid supports equality/inequality testing a value against `blank` or `empty`. In this way, Liquid allows the author to ask, "is this value blank?", or "is this value empty?"

#### Blank

Quoting from the [Rails API](https://api.rubyonrails.org/classes/Object.html#method-i-blank-3F):

> An object is blank if it's false, empty, or a whitespace string. For example, `nil`, '', ' ', \[], {}, and `false` are all blank.

```liquid
{% assign empty_string = "" %}
{% assign whitespace_string = "  " %}
{% assign non_blank_string = "  !!  " %}
{% assign non_empty_array = "1,2,3" | split: "," %}
{% assign empty_hash = hash %}

{% comment %}
  The following `if` statements all pass.
{% endcomment %}
{% if empty_string == blank %}
{% if whitespace_string == blank %}
{% if non_blank_string != blank %}
{% if non_empty_array != blank %}
{% if empty_hash == blank %}
```

#### Empty

An array, hash, or string can be tested for emptiness. An array is empty if it has no elements; a hash is empty if it has no key-value pairs; a string is empty if its length is zero.

{% hint style="info" %}
A string that only contains whitespace is not empty, but it *is* blank!
{% endhint %}

```liquid
{% assign empty_string = "" %}
{% assign whitespace_string = "  " %}
{% assign non_blank_string = "  !!  " %}
{% assign non_empty_array = "1,2,3" | split: "," %}
{% assign empty_hash = hash %}

{% comment %}
  The following `if` statements all pass.
{% endcomment %}
{% if empty_string == empty %}
{% if whitespace_string != empty %}
{% if non_blank_string != empty %}
{% if non_empty_array != empty %}
{% if empty_hash == empty %}
```

## Contains operator

The `contains` operator is used to check for the existence of a substring in a string, or for a specific element in an array.

### Substring containment

```liquid
{% if email_domain contains "@" %}
  {% error "Do not include '@' symbols in email domains. Thanks!" %}
{% endif %}
```

### Array element containment

```liquid
{% assign product_tags = "foo, bar, baz" | split: ", " %}
{% assign product_is_tagged_bar = false %}

{% if product_tags contains "bar" %}
  {% assign product_is_tagged_bar = true %}
{% endif %}
```

## Logical operators

Liquid has two logical operators: `and` and `or`.

If `b = 3` and `c = 6`, the table below illustrates the logical operators in Liquid, and the way they interact with `b` and `b`:

| Operator | Example           | Result  |
| -------- | ----------------- | ------- |
| `and`    | `b < 2 and c < 6` | `false` |
| `or`     | `b < 2 or c < 6`  | `true`  |

### Check if both the shipping address and billing are blank

```liquid
{% if order.shipping_address != blank and order.billing_address != blank %}
  {% comment %} do something {% endcomment %}
{% endif %}
```

### Check if tag equals blank or a customer's tags contains a certain tag

```liquid
{% if tag == blank or customer.tags contains tag %}
  {% comment %} do something {% endcomment %}
{% endif %}
```