---
url: /process-functions/mapping-findusingleft.md
description: Finds the mapping rows that match the given left keys.
---

# mapping.findUsingLeft

Finds the mapping rows that match the given left keys.

```js
mapping.findUsingLeft(mappingName, leftKeys)
```

## Parameters

| Parameter | Type | Description |
|---|---|---|
| `mappingName` | `string` | The mapping's name or id. |
| `leftKeys` | `string[]` | One element for each dimension on the left side, in order. |

## Returns

The matching rows as a JSON string, read with `JSON.parse()`. It's always an array, even when only one row matches, and each row has its `id`, `left` keys and `right` keys. Returns `null` when no row matches. To get a single row instead, use [mapping.findFirstUsingLeft](/process-functions/mapping-findfirstusingleft).

## Examples

::: code-group

```js [find.js]
const rows = JSON.parse(mapping.findUsingLeft("Time to Year and Month", ["FY2017 - Jul"]));
console.log(rows);
```

```json [Output]
[
    {
        "id": 1,
        "left": ["FY2017 - Jul"],
        "right": ["2017", "Jul"]
    }
]
```

:::

## Related

* [mapping.findUsingRight](/process-functions/mapping-findusingright)
* [mapping.rowUpdate](/process-functions/mapping-rowupdate)
* [mapping.rowDelete](/process-functions/mapping-rowdelete)