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  • License MIT

Get accurate and well named css box model information about an Element 📦

Package Exports

  • css-box-model

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 (css-box-model) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

css-box-model 📦

Get accurate and well named CSS Box Model information about a Element.

Build Status npm dependencies Downloads per month min minzip

Any time you are using Element.getBoundingClientRect() you might want to consider using css-box-model instead to get more detailed box model information.

Usage

// @flow
import { getBox } from 'css-box-model';

const el: HTMLElement = document.getElementById('foo');
const box: BoxModel = getBox(el);

// profit

Installation

## yarn
yarn add css-box-model

# npm
npm install css-box-model --save

The CSS Box Model

the box model

Box type Composition
Margin box margin + border + padding + content
Border box border + padding + content
Padding box padding + content
Content box content

This our returned BoxModel:

export type BoxModel = {|
  // content + padding + border + margin
  marginBox: Rect,
  // content + padding + border
  borderBox: Rect,
  // content + padding
  paddingBox: Rect,
  // content
  contentBox: Rect,
  // for your own consumption
  border: Spacing,
  padding: Spacing,
  margin: Spacing,
|};

// Supporting types

// This is an extension of DOMRect and ClientRect
export type Rect = {|
  // ClientRect
  top: number,
  right: number,
  bottom: number,
  left: number,
  width: number,
  height: number,
  // DOMRect
  x: number,
  y: number,
  // Rect
  center: Position,
|};

export type Position = {|
  x: number,
  y: number,
|};

export type Spacing = {
  top: number,
  right: number,
  bottom: number,
  left: number,
};

API

getBox

(el: HTMLElement) => BoxModel

Use getBox to return the box model for an element

withScroll

(original: BoxModel, scroll?: Position = getWindowScroll()) => BoxModel

This is useful if you want to know the box model for an element relative to a page

const el: HTMLElement = document.getElementById('app');
const box: BoxModel = getBox(el);
const withScroll: BoxModel = withScroll(box);

You are welcome to pass in your own scroll. By default we we use the window scroll:

const getWindowScroll = (): Position => ({
  x: window.pageXOffset,
  y: window.pageYOffset,
});

calculateBox

(borderBox: AnyRectType, styles: CSSStyleDeclaration) => BoxModel

This will do the box model calculations without needing to read from the DOM. This is useful if you have already got a ClientRect / DOMRect and a CSSStyleDeclaration as then we can skip computing these values.

const el: HTMLElement = document.getElementById('app');
const borderBox: ClientRect = el.getBoundingClientRect();
const styles: CSSStyleDeclaration = window.getComputedStyles(el);

const box: BoxModel = calculateBox(borderBox, styles);

AnyRectType allows for simple interoperability with any rect type

type AnyRectType = ClientRect | DOMRect | Rect | Spacing;

createBox

({ borderBox, margin, border, padding }: CreateBoxArgs) => BoxModel

Allows you to create a BoxModel by passing in a Rect like shape (AnyRectType) and optionally your own margin, border and or padding.

type CreateBoxArgs = {|
  borderBox: AnyRectType,
  margin?: Spacing,
  border?: Spacing,
  padding?: Spacing,
|};
const borderBox: Spacing = {
  top: 10,
  right: 100,
  left: 20,
  bottom: 80,
};
const padding: Spacing = {
  top: 10,
  right: 20,
  left: 20,
  bottom: 10,
};

const box: BoxModel = createBox({ borderBox, padding });

Utility API

Functions to help you interact with the objects we provide

getRect

(spacing: AnyRectType) => Rect

Given any Rect like shape, return a Rect. Accepts any object that has top, right, bottom and right (eg ClientRect, DOMRect);

const spacing: Spacing = {
  top: 0,
  right: 100,
  bottom: 50,
  left: 50,
};

const rect: Rect = getRect(spacing);

console.log(rect);

/*
{
  top: 0,
  right: 100,
  bottom: 50,
  left: 50,
  width: 100,
  height: 50,
  x: 0,
  y: 0,
  center: { x: 50, y: 50 },
}
*/

expand

Used to expand a Spacing

(target: Spacing, expandBy: Spacing) => Spacing;
const original: Spacing = {
  top: 10,
  left: 11,
  right: 21,
  bottom: 22,
};

const expandBy: Spacing = {
  top: 1,
  left: 2,
  right: 3,
  bottom: 4,
};

const expanded: Spacing = expand(original, expandBy);

console.log(expanded);

/*
{
  // pulled back
  top: 8,
  left: 8
  // pushed forward
  bottom: 22,
  right: 22,
}
*/

shrink

Used to shrink a Spacing

(target: Spacing, shrinkBy: Spacing) => Spacing;
const original: Spacing = {
  top: 10,
  left: 10,
  right: 20,
  bottom: 20,
};

const shrinkBy: Spacing = {
  top: 2,
  left: 2,
  right: 2,
  bottom: 2,
};

const smaller: Spacing = shrink(original, shrinkBy);

console.log(smaller);

/*
{
  // pushed forward
  top: 12,
  left: 12
  // pulled back
  bottom: 18,
  right: 18,
}
*/