Package Exports

attrpath
attrpath/dist/esm/index.js
attrpath/dist/index.js

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (attrpath) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

AttrPath

Object Attribute Path Traverser. Safely traverse the javascript attribute tree using a text path representation. You can also check the existence of the path.

GitHub package.json version npm type definitions GitHub GitHub last commit

README　DEMO　in detail

Motivation

For example, I didn't like to write the following code every time...　humm...

const value = {
    children: {
        john: {hobby: [{name: "Cycling"}, {name: "Dance"}], pet: [{type: "dog", name: "Max"}]},
        tom: {hobby: [{name: "Squash"}], pet: [{type: "cat", name: "Chloe"}]}
    }
};

var answer = undefined;
if (value.children) {
    if (value.children.john) {
        if (value.children.john.hobby) {
            if (Array.isArray(value.children.john.hobby)) {
                if (value.children.john.hobby.length >= 2) {
                    if (value.children.john.hobby[1].name) {
                        answer = value.children.john.hobby[1].name;
                    }
                }
            }
        }
    }
}

or

answer = value?.children?.john?.hobby[1]?.name;

The ugly thing above is nice if you can write it like this, right?

const {AttrPath}: any = require("attrpath");

var answer = AttrPath.traverse(value, ".children.john.hobby[1].name");

Features

Safely traverse the object path using the given path string. Also, an array may be included in the middle of the path.

Installation

npm install atttrpath

No modules depend on it.

Usage

API

const {AttrPath}: any = require("attrpath");
// or
import {AttrPath} from 'attrpath';

traverse value.

AttrPath.traverse(object, path [default_value]);

params

params	meaning
object: any	Target Object.
path: string	Traverse path.　The beginning of the path is "." or "[".
e.g.	".cat.eye.left", ".dog['leg'][1].pad" , etc...
default_value: any	The value to return if there is no corresponding value in the object path. default is "undefined".
default_value: function	If you give a function, give the traverse result to the first argument of the function.

result

result	meaning
result: any	Objects obtained as a result of traverse.

path is grammatically valid?

AttrPath.is_valid(path);

params

params	meaning
path: string	Traverse path.

result

result	meaning
result: boolean	path is grammatically correct?

Default Value

If the result is Undefined, the default value is returned.

const {AttrPath} = require('attrpath');

    AttrPath.traverse({}, '.path', 1);

Example

const {AttrPath}: any = require("attrpath");

const value = {
    children: {
        john: {
            hobby: [{name: "Cycling"}, {name: "Dance"}],
            pet: [{type: "dog", name: "Max"}]
        },
        tom: {
            hobby: [{name: "Squash"}],
            pet: [{type: "cat", name: "Chloe"}]
        }
    }
};

console.log(AttrPath.traverse(value, '.children.john.hobby[0].name'))

> "Max"

console.log(AttrPath.traverse(value, '.children.john.hobby[1].name'))

> undefined


const Default = (n:any) => {
    console.log(n);
}

AttrPath.traverse(value, '.children.john.hobby[0].name', Default)

> "Max"

console.log(AttrPath.is_valid('.children.john.hobby[0].name'))

> true

console.log(AttrPath.is_valid('.children.john.hobby[0]..name'))

> false

more Example

class Klass {
    member = "name";

    Member() {
        return AttrPath.traverse(this, '.member');
    }
}

const klass = new Klass();
console.log(klass.Member())

> "name"

class ParentKlass {
    member = "name";
}

class SubKlass extends ParentKlass {
    Member() {
        return AttrPath.traverse(this, '.member');
    }
}

const sub_klass = new SubKlass();
console.log(sub_klass.Member())

> "name"

Example Data

    const value = {
        children: {
            john: {
                hobby: [{name: "Cycling"}, {name: "Dance"}],
                pet: [{type: "dog", name: "Max"}]
            },
            tom: {
                hobby: [{name: "Squash"}],
                pet: [{type: "cat", name: "Chloe"}]
            }
        }
    };

ESModule

import {AttrPath} from 'attrpath';

    AttrPath.traverse(value, '.children')
    AttrPath.is_valid('.children["john"].hobby[1].name')

CommonJS

const {AttrPath} = require('attrpath');

    AttrPath.traverse(value, '.children');
    AttrPath.is_valid('.children["john"].hobby[1].name')

Array

The original value can be an array.

const {AttrPath} = require('attrpath');

    AttrPath.traverse([1], '[0]');

Undefined

Returns Undefined if the original value is not an object.

const {AttrPath} = require('attrpath');

    AttrPath.traverse(null, '.path');
    AttrPath.traverse(undefined, '.path');
    AttrPath.traverse(false, '.path');
    AttrPath.traverse(true, '.path');
    AttrPath.traverse(NaN, '.path');
    AttrPath.traverse(Infinity, '.path');
    AttrPath.traverse(0, '.path');
    AttrPath.traverse(-1, '.path');
    AttrPath.traverse("", '.path');
    AttrPath.traverse("1", '.path');
    AttrPath.traverse([1], '.path');
    AttrPath.traverse({}, '.path');

Known Bug

If the key contains "." as shown below, it will not work properly.

    const value = {
        "children.john": {
                hobby: [{name: "Cycling"}, {name: "Dance"}],
                pet: [{type: "dog", name: "Max"}]
            }
    };

    NG:
    AttrPath.traverse(value, ".'children.john'");

Note

See demo.md for unclear cases.

Author

info@seventh-code.com

License

"AttrPath" is under MIT license.