follows-order
v1.0.0 array elements order ordered sequence sort sorted check validate and 3 more...
follows-order
Checks that specific array elements or string characters appear only in a certain order. Packaged as a Node.js module.
Installation
npm install follows-order --save
The module exposes a single function.
Usage
Array Example
const followsOrder = require('follows-order')
const data = {
name: "Test",
description: "This is a test",
module: "follows-order",
}
// Check to make sure that `name` precedes `description`.
// (Note: JavaScript does not guarantee object key order.
// This is only for the sake of example.)
followsOrder(Object.keys(data), ['name', 'description']) // true
String Example
const followsOrder = require('follows-order')
const data = 'test'
// Does the first "t" come before the first "e"?
followsOrder(data, 'te') // true
A Note on Duplicates
If an array or string is being checked to see if its order follows [A, B], then the first B cannot appear before the first A does, even if the [A, B] pattern occurs later.
This is according to design: the module is made to enforce a certain order, not merely check for a pattern.
Data | Order | Result | Reason |
---|---|---|---|
[B,A,B] | [A,B] | Fail | The first instance of A should have preceded the first instance of B. |
[A,B,B,A] | [A,B] | Pass | A and B only occur once in the order, so only the first instances in the data are checked. |
[A,B,B,A] | [A,B,A,B] | Fail | A and B occur twice in the order, so the second A in the data should have preceded the second B. |
const followsOrder = require('follows-order')
const data = [1, 2, 1]
followsOrder(data, [1, 2]) // true
followsOrder(data, [2, 1]) // false, because in the data the first instance of 1 occurs before 2
followsOrder(data, [1, 2, 1]) // true
If you don’t want to deal with duplicate elements in your data, you’ll need to deduplicate the data yourself before you check it with follows-order
.