1.0.4 • Published 2 years ago
@aircall/expression-parser v1.0.4
expression-parser
Resolves templated expressions in a secure local scope.
resolveExpression function
Arguments:
expression: expression templated stringcontext(optional): context from where to resolve expressionsoptions(optional): parser options:passContextToEmptyFunctions?: boolean(defaulttrue): Allow to pass the context object into empty functions calls in single expression strings. Anonymous functions are not supportedtransformArrayNegativeIndex?: boolean(defaulttrue): Allow and parse negative indexes correctly
Example:
import { resolveExpression } from '@aircall/expression-parser'
const template = 'Start: ${variable.start}, End ${variable.end}'
const context = {
start: '09:00',
end: '12:00',
}
resolveExpression(template, context);
// returns 'Start: 09:00, End 12:00'There are some use cases in the E2E tests
Default expression handling
Default expressions come in the form of ${<JavaScript code to evaluate>}. The templates are
delimited with ${ and } strings and all the JavaScript code inside will be evaluated. If there
is more than one expression or there is some text around the template, it will return a string
evaluating all of them.
For example, with this context:
{
content: {
input: 2,
id: 'operation',
executionId: 1234,
},
environment: {
variables: {
input: 1,
inputArray: [1, 2, 3],
inputObject: {
'spaced name': 'name'
},
getInput: (context) => {
return context.environment.variables.input;
},
isBelow: (a, b) => a < b,
commonVariablePrefix: "a",
current: 2,
},
}The following expressions are supported:
| Template | Result | More information |
|---|---|---|
${environment.variables.input} | 1 | |
${environment.variables.inputArray[0]} | 1 | resolves to first item of the variable input array |
${environment.variables.inputArray[-1]} | 3 | resolves to last item of the variable input array |
${environment.variables.inputObject['spaced name']} | 'name' | resolves to the variable input object property spaced name |
${environment.services.getInput()} | 1 | executes the service function getInput with the context passed as an argument |
${environment.services.getInput} | Function getInput() | returns the service function |
${environment.services.isBelow(content.input,2)} | false | executes the service function isBelow with content.input value and 2 |
I, ${content.id}, execute with id ${content.executionId} | 'I, operation, execute with id 1234' | formats a string getting content object values |
${true} | true | |
${false} | false | |
${null} | null | |
${undefined} | undefined | |
${<number>} | <number> | returns the number passed |
${() => {}} | () => {} | returns the lambda function |
It is possible to nest multiple expressions if you write them in proper JavaScript code. For example:
Given this context:
{ environment: { variables: { a1: (v) => `method a1: ${v}`, a2: (v) => `method a2: ${v}`, a3: (v) => `method a3: ${v}`, }, commonVariablePrefix: "a", current: 2, }, };The expression
${environment.variables[`${environment.commonVariablePrefix}${environment.current}`]}returns the function:
(v) => `method a2: ${v}`