dom-step

Install

npm install --save dom-step

Usage

import step from 'dom-step';
let list = document.querySelector('ol').children;
let one = list[0];
let two = step(one, 'down');
console.log(one.innerHTML); //One
console.log(two.innerHTML); //Two

About

DOM traversal is usually restricted to parent/child relationships, or child/child relationships. dom-step traverses elements by the visual position of elements.

step(element, direction, options)

element is what ever DOM element that has sibling elements.

direction is a word string that is one of these directions:

• left
• up
• right
• down

options.range

options.range should be set as an integer. The default for options.range is 1.

Set options range to define how close the sibling element needs to be to the original element to be considered visually directly left, up, right, or down. In this way options.range is considered to be a restricting value.

import step from 'dom-step';
let list = document.querySelector('ol').children;
let one = list[0];
let two = step(one, 'down', {range: 10});
console.log(one.innerHTML); //One
//The margin between list[0], and list[1] is 11 so
console.log(two); //undefined

Hint: Some styles like display: inline, or display: inline-block are whitespace dependent. Any whitespace around the element set to these display values will make it appear to have a margin that doesn't actually exist. Increase options.range, or iterate children to remove text node whitespace around elements to fix this.

Algorithm

Note: This algorithm was abandoned in version 2. It is still somewhat relevant. The target next element would still be in the same position. Version 2 uses document.elementFromPoint(x, y) instead to find nearby elements.

dom-step finds the nearest sibling element in the DOM. It does this by first checking the element.nextElementSibling, or element.previousElementSibling for down/right, or up/left respectively. Failing that it then checks other elements using a naive linear search through the rest of the siblings in the appropriate direction.

To summarize the defaults:

"down"/"right" = closest next sibling to the down, or right

"up"/"left" = closest previous sibling to the up, or left

Visual Representation

The black box is the orignal element passed to step(element, 'up', {range: 10}). In this case "up" was the direction chosen.

The red box is not returned. The green box is returned from step().

The purple dotted lines represent the left/right range a sibling box must be in to be chosen.

The blue rectangle is the range a sibling must overlap to be chosen.

The gold lines represent the boundary a sibling element must cross in order to be chosen.

At the intersection of the purple lines, gold lines, and blue rectangle a sibling element is selected.

options.traverse

Version 2 uses elementFromPoint so traversal isn't required. options.traverse does nothing.

options.wrap

options.wrap was introduced in version 2.

Set options.wrap to an integer greater than 0 to activate wrapping.

Wrapping happens when the direction you choose crosses the edge of the parent of the element you pass to domStep.

For instance:

import step from 'dom-step';
let list = document.querySelector('ol').children;
let one = list[0];
//'up' will go outside of the parent
let two = step(one, 'up', {wrap: 10});
console.log(one.innerHTML); //One
//If the list has three elements
console.log(two.innerHTML); //Three