---
url: /process-functions/mapping-findusingleft.md
description: Finds a mapping row by its left keys.
---

# mapping.findUsingLeft

Finds a mapping row by its 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 row as a JSON string, with its `id`, `left` keys and `right` keys. Use `JSON.parse()` to read it. Returns `null` when no row matches.

## Examples

::: code-group

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

```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)