# Revision history [back]

### How to use field path expression ?

thanks.... I want to use field replacer to replace a field's value . value, but the field is undefined,in fields undefined. The field's content is /[${f:path() /*[${f:path() == '/control/switch/on' && f:value() == '1'}],but  but it's not working.....Please working. Please help me with this Instead, when I'm trying this.

When I try with /[${f:path() /*[${f:path() == '/control' && f:value() == '1'}] is working it works for the field replacer, which is not my expectation field name.expectation.

### How to use field path expression ?

I want to use field replacer to replace a field's value, but the field is undefined. The field's content is /*[${f:path() == '/control/switch/on' && f:value() == '1'}] but it's not working. Please help me with this. When I try with /*[${f:path() == '/control' && f:value() == '1'}] it works for the field replacer, which is not my expectation.

I want to change corresponding values according to different paths and values, eg:

input:

{"control":{"power":0}}


output:

{"control":{"power":"off"}}


or input

{"control":{"power":1}}


output:

{"control":{"power":"on"}}