Defaults Object

Defaults Object | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Data Processing
Input types: textarea
Output type: text
Sample coverage: 4
API ready: Yes

Overview

The Defaults Object tool allows you to efficiently populate missing properties in a JSON object by merging it with one or more source objects using the lodash _.defaults method.

When to use

When you need to ensure an object has required keys without overwriting existing data.
When merging configuration objects where user-defined settings should take precedence over defaults.
When cleaning up incomplete data structures by filling in missing fields with predefined values.

How it works

1Input your primary target JSON object into the target field.
2Provide one or more source objects containing the default values you wish to apply.
3The tool processes the objects, assigning values from sources only to properties that are currently undefined in the target.
4The resulting JSON object is returned with all missing properties filled.

Use cases

Applying default configuration settings to a user's partial preferences object.
Filling in missing API response fields with fallback values to prevent runtime errors.
Standardizing data objects by ensuring all expected keys exist with default values.

Examples

1. Applying App Configuration Defaults

Frontend Developer

Background

An application receives a partial user settings object from local storage.

Problem

The app needs to ensure 'theme' and 'notifications' keys exist, but must not overwrite the user's existing 'theme' choice.

How to use

Paste the user's object into 'Target Object' and the default settings into 'Source 1'.

Target: {"theme": "dark"} | Source 1: {"theme": "light", "notifications": true}

Outcome

The result is {"theme": "dark", "notifications": true}, preserving the user's theme while adding the missing notification setting.

2. Standardizing API Data

Backend Engineer

Background

A legacy database returns objects missing several new fields required by the frontend.

Problem

The frontend crashes when accessing undefined properties in the data objects.

How to use

Use the tool to merge the database object with a source object containing the new default values.

FAQ

Does this tool overwrite existing values?

No, it only assigns values to properties that are undefined in the target object.

What happens if multiple sources have the same key?

The tool applies sources in order; earlier sources take precedence over later ones for the same undefined property.

Which library does this tool use?

It utilizes the lodash _.defaults function for reliable object merging.

Can I use this for nested objects?

This tool performs a shallow merge; it assigns values to top-level undefined properties.

Is the input format strictly JSON?

Yes, the tool expects valid JSON objects in the input fields.

Target: {"id": 101} | Source 1: {"status": "active", "retryCount": 0}

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Applying App Configuration Defaults

2. Standardizing API Data

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