I am working on a custom error constructor for my seed project. I had a few objectives in mind when I started.
Technically inspired by this post.
| var util = require('util'); | |
| function colorize (str, color) { | |
| var options = { | |
| red: '\u001b[31m' | |
| , green: '\u001b[32m' | |
| , yellow: '\u001b[33m' | |
| , blue: '\u001b[34m' | |
| , magenta: '\u001b[35m' | |
| , cyan: '\u001b[36m' | |
| , gray: '\u001b[90m' | |
| , reset: '\u001b[0m' | |
| }; | |
| return options[color] + str + options.reset; | |
| }; | |
| function pad (str, width) { | |
| return Array(width - str.length).join(' ') + str; | |
| }; | |
| module.exports = CustomError; | |
| function CustomError (msg) { | |
| Error.call(this); | |
| // Write our opts to the object | |
| this.message = msg; | |
| this.name = 'CustomError'; | |
| this.memory = process.memoryUsage(); | |
| // We need the raw stack so we can make a JSON | |
| // object for writing to the logs. | |
| var orig = Error.prepareStackTrace; | |
| Error.prepareStackTrace = function(_, stack){ return stack; }; | |
| Error.captureStackTrace(this, arguments.callee); | |
| this.__stack = this.stack; | |
| Error.prepareStackTrace = orig; | |
| // Lets make our JSON object. | |
| this._stack = []; | |
| for (var i = 0; i < this.__stack.length; i ++) { | |
| var frame = this.__stack[i]; | |
| this._stack.push({ | |
| filename: frame.getFileName() | |
| , typename: frame.getTypeName() | |
| , linenum: frame.getLineNumber() | |
| , funcname: frame.getFunctionName() | |
| , method: frame.getMethodName() | |
| }); | |
| } | |
| // Since we provided our own prepareStackTrace, we need | |
| // to provide a new stack getter for display. Lets make | |
| // it look better while we are at it. | |
| Object.defineProperty(this, 'stack', { | |
| get: function () { | |
| var buf = []; | |
| buf.push(''); | |
| buf.push(pad('', 8) + colorize(this.name, 'red')); | |
| buf.push(pad('', 8) + colorize(Array(this.name.length + 1).join('-'), 'gray')); | |
| buf.push(pad('', 8) + colorize(this.message, 'magenta')); | |
| buf.push(pad('', 8) + colorize((this.memory.heapTotal / 1048576).toFixed(3) + ' MB', 'blue') + colorize(' total ', 'gray')); | |
| buf.push(pad('', 8) + colorize((this.memory.heapUsed / 1048576).toFixed(3) + ' MB', 'blue') + colorize(' used ', 'gray')); | |
| buf.push(pad('', 8) + colorize(Array(this.name.length + 1).join('-'), 'gray')); | |
| buf.push(''); | |
| this._stack.forEach(function (frame) { | |
| buf.push(' ' + colorize(pad(frame.linenum + '', 5), 'blue') + colorize(' ' + frame.filename, 'gray') ); | |
| buf.push(pad('', 8) + colorize((frame.funcname ? frame.funcname : 'Anonymous'), 'green') + ' ' + colorize('[' + frame.typename + ']', 'yellow')); | |
| }); | |
| buf.push(''); | |
| return buf.join('\n'); | |
| } | |
| }); | |
| } | |
| util.inherits(CustomError, Error); | |
| CustomError.prototype.toJSON = function () { | |
| return { | |
| name: this.name | |
| , message: this.message | |
| , memory: this.memory | |
| , stack: this._stack | |
| }; | |
| } |
| var CustomError = require('./customerror'); | |
| function log (err) { | |
| console.error(err); | |
| } | |
| function a (){ | |
| b(); | |
| } | |
| function b () { | |
| var err = new CustomError('There was a problem doing something in your app.'); | |
| log(err.toJSON()); | |
| throw err; | |
| } | |
| a(); |
I understand that you have to define the
stackproperty because you overriddenError.prepareStackTrace.If you don't really need to custom format the stack, you can try to do as follows
I used this chunk of code on node-error and it works.