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--- |
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title: Expressions common issues |
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description: Documentation for common issues and questions related to expressions in n8n, a workflow automation platform. Includes details of the issue and suggested solutions. |
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contentType: howto |
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--- |
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# Expressions common issues |
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Here are some common errors and issues related to [expressions](/code/expressions.md) and steps to resolve or troubleshoot them. |
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## The 'JSON Output' in item 0 contains invalid JSON |
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This error occurs when you use JSON mode but don't provide a valid JSON object. Depending on the problem with the JSON object, the error sometimes display as `The 'JSON Output' in item 0 does not contain a valid JSON object`. |
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To resolve this, make sure that the code you provide is valid JSON: |
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- Check the JSON with a [JSON validator](https://jsonlint.com/). |
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- Check that your JSON object doesn't reference undefined input data. This may occur if the incoming data doesn't always include the same fields. |
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## Can't get data for expression |
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This error occurs when n8n can't retrieve the data referenced by an expression. Often, this happens when the preceding node hasn't been run yet. |
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Another variation of this may appear as `Referenced node is unexecuted`. In that case, the full text of this error will tell you the exact node that isn't executing in this format: |
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> An expression references the node '<node-name>', but it hasn’t been executed yet. Either change the expression, or re-wire your workflow to make sure that node executes first. |
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> |
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To begin troubleshooting, test the workflow up to the named node. |
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For nodes that use JavaScript or other custom code, you can check if a previous node has executed before trying to use its value by checking the following: |
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```javascript |
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$("<node-name>").isExecuted |
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``` |
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As an example, this JSON references the parameters of the input data. This error will display if you test this step without connecting it to another node: |
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```javascript |
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{ |
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"my_field_1": {{ $input.params }} |
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} |
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``` |
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## Invalid syntax |
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This error occurs when you use an expression that has a syntax error. |
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For example, the expression in this JSON includes a trailing period, which results in an invalid syntax error: |
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```jsx |
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{ |
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"my_field_1": "value", |
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"my_field_2": {{ $('If').item.json. }} |
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} |
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``` |
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To resolve this error, check your [expression syntax](https://www.notion.so/code/expressions/) to make sure they follow the expected format. |
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