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npm version
rangeblock is a JavaScript library that makes it easy to locate, measure, and represent layouts of text ranges in a web page.

It provides a more precise function than Element.getClientRects() which returns dimensions for each border box.

Why do I need it?

rangeblock does 2 things for you:
  • It gives you detailed layout information of a range of text in the form of an array of dimensions, each representing a line or block of text.

  • It provides a text representation for Range objects in the format of unique path, so that you can persistant the range. Then you can save it on server or shared it across users and browsers.

How is it useful?

Its possible application is quite open-ended. For example,
  • build non-intrusive web annotation browswer plug-ins
- hlc
  • add annotation functions to your existing webistes
  • create high-precision text locator extensions


npm install rangeblock --save


// TypeScript
import * as rb from "rangeblock"

// measure layouts
let block = rb.extractSelectedBlock(window, document);
if (!block){
  console.error("please select some text on the web page");
console.info("Text layout: " + JSON.stringify(block.dimensions));

// representation of the text range 
console.info("Text layout: " + JSON.stringify(block.rangeMeta));

// recreate range using RangeMeta
let meta :RangeMeta = ... ; 
block = rb.restoreBlock(window, document, meta);

Unique Path

We define a text format called Unique Path to uniquely locate a node in a static DOM tree. It is formally described as
UPath = [/|#<id>]([/<nodeIndex>])+

Known Issue

Text kerning is not considered in current implementation. If you have a good suggestion, welcome to submit an issue or pull request.