propath

Access deep property-values, arrays and functions using a path. Written in TypeScript. Paths are parsed for performance.

Install

Node.js

npm install propath --save

Usage

import pp from "propath";

const obj = {
  a: {
    b: "f",
    c: ["g", "h"],
    d: () => 'i',
    e: j => `${j}_k`,
  },
};

// Parse path
const ab = pp('a.b');

// Get value
let value = ab.get(obj); // value === "f"

// Return undefined if path doesn't exist
const alm12 = pp('a.l.m[12]');
value = alm12.get(obj); // typeof value === "undefined"
    
// Return predictable value if path doesn't exist
const ano0pOrHello = pp('a.n.o[0].p()', 'Hello');
value = ano0pOrHello.get(obj); // value === "Hello"

// Set value
ab.set(obj, "l");
value = ab.get(obj); // value === "l"

// Has value
let hasAB = ab.has(obj); // hasAB === true
const hasABC = pp('a.b.c').has(obj); // hasABC === false

// Delete value
ab.delete(obj); // returns true if ab was found and deleted
hasAB = ab.has(obj); // hasAB === false

// Get value from array
const ac0 = pp('a.c[0]');
value = ac0.get(obj); // value === "g"
value = pp('a.c[1]').get(obj); // value === "h"

// Set value on array
ac0.set(obj, 'm');
value = ac0.get(obj); // value === "m"

// Get value from function
const ad = pp('a.d()');
value = ad.get(obj) // value === "i"

// Get value from parametrized function
const param = 'n';
value = pp(`a.e("${param}")`).get(); // value === "n_k"
// -> Parameters are provided in JSON syntax

How propath deals with inherited properties

Propath doesn't differentiate between inherited and own properties.

Full API + examples

Import propath

import pp from "propath";

Parse property-path / instantiate propath

const ab = pp<V, D>('a.b', 'DEFAULT');

• Type V is the value type, the path is expected to return
• Type D is the value type of the default value

Default value parameter is optional.

Property-path syntax

Value access

a.b.c.d.e

Values access is done by property-names separated by dots ..

Array index

a.b[5]

Value access is done by index number in square brackets [ and ].

Function call

a.b.c()
a.b.c("STRING", 6.7, false)

Calling functions is done by parameters in round brackets ( and ).

• Function calls cannot be nested, but can contain whitespace.
• Parameters must be in JSON syntax, strings must be double quoted with "

API

pp<T, D>(path :string, defaultValue :D) :<instance>

If propath is imported as the name pp, it is called as a function with optional type parameters T specifying the type returned by the path and D specifying the type of the default value.

• D can be omitted while T is provided.
• Neither T nor D must be provided.
• If T is omitted, return-type of .get will be any.
• Default value can be omitted.

.get(<obj>) :T|any|D|undefined

Traverses the path, returns the value found in <obj> if the path can be traversed completely. If it cannot, the default value or undefined is returned.

.set(<obj>, value) :boolean

Traverses the path, sets the value if the path can be traversed completely in <obj>. If it cannot, false is returned.

.has(<obj>) :boolean

Traverses the path, return true if the path can be traversed completely in <obj>. If it cannot, false is returned.

.delete(<obj>) :boolean

Traverses the path, deletes the value and returns true if the path can be traversed completely in <obj>. If it cannot, false is returned.