glsldoc is a JSON-structured documentation of all WebGL GLSL predefined functions, constants, types, qualifiers,... port from the GLSL ES Specification.
GLSL documentation is maintained in this Google Spreadsheet and exported to JSON using this script.
It can be used to add contextual documentation to your GLSL editor.
npm install glsldoc
then you can:
var Documentation = require("glsldoc");
console.log(Documentation);
https://github.com/glslio/glsl.io/blob/master/client/src/screens/editor/GlslContextualHelp/index.js