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# Error: error:badmember
Syntax error in param value using @member lookup

    Dotted member path "@{0}" is invalid.

## Description

Occurs when there is a syntax error when attempting to extract a param value from the data object.

Here's an example of valid syntax for `params` or `paramsDefault`:

    {
    bar: '@foo.bar'
    }

The part following the `@`, `foo.bar` in this case, should be a simple dotted member lookup using only ASCII identifiers. This error occurs when there is an error in that expression. The following are all syntax errors

Value | Error
--- | ---
`@` | Empty expression following `@`.
`@1.a` | `1` is an invalid javascript identifier.
`@.a` | Leading `.` is invalid.
`@a[1]` | Only dotted lookups are supported (no index operator)