Bug 157246

Specifically, the library mathjs (see http://mathjs.org and https://github.com/josdejong/mathjs) uses an idiom where it created literal objects with property names that look like this: 'number | BigNumber | Unit'. Later, this name is used in a string to create function source code that gets eval'ed. Since 'number | BigNumber | Unit' is not a valid function name, we get a syntax error. The nitty gritty details: 1. mathjs uses object literals with the funky property names for its function members. For example, // helper function to type check the middle value of the array var middle = typed({ 'number | BigNumber | Unit': function (value) { return value; } }); 2. mathjs' getName() uses Function.name to get the name of functions (hence, picks up the ES6 behavior): /** * Retrieve the function name from a set of functions, and check * whether the name of all functions match (if given) ... */ function getName (fns) { var name = ''; for (var i = 0; i < fns.length; i++) { var fn = fns[i]; ... name = fn.name; ... return name; } 3. mathjs uses that name to assembler new function source code that gets eval'ed: /** * Compose a function from sub-functions each handling a single type signature. ... */ function _typed(name, signatures) { ... // generate code for the typed function var code = []; var _name = name || ''; ... code.push('function ' + _name + '(' + _args.join(', ') + ') {'); code.push(' "use strict";'); code.push(' var name = \'' + _name + '\';'); code.push(node.toCode(refs, ' ')); code.push('}'); // generate body for the factory function var body = [ refs.toCode(), 'return ' + code.join('\n') ].join('\n'); // evaluate the JavaScript code and attach function references var factory = (new Function(refs.name, 'createError', body)); // <========= Syntax Error right here! var fn = factory(refs, createError); ... return fn; } Until mathjs (and any other frameworks that does similar things) and sites that uses mathjs has been updated to work with ES6, we'll need a compatibility hack to work around it.