loadSrcLocation.js

'use strict';

const loadSrcLocation = (locationStr, contextRadius = 5) => {
  const parts = locationStr.split(':');
  const col = Number(parts[parts.length - 1]);
  const lineNo = Number(parts[parts.length - 2]);
  const url = parts.slice(0, parts.length - 2).join(':');
  
  return fetch(url)
    .then(res => res.text())
    .then(text => {
      const lines = text.split('\n');
      
      const contextLines = lines
        .slice(lineNo - contextRadius, lineNo + contextRadius + 1)
        .map((line, i) => `${lineNo - contextRadius + i}: ${line}`)
      ;
      
      contextLines.splice(contextRadius, 0, '~'.repeat(`${lineNo}: `.length + col - 1) + '^');
      
      return contextLines.join('\n');
    })
  ;
};