When I use the JSC (JavaScriptCore) engine provided in the System Library, it acts differently then when using Safari's debug console

$ /System/Library/Frameworks/JavaScriptCore.framework/Versions/A/Resources/jsc
>>> console.log("hello");
Exception: TypeError: undefined is not an object (evaluating 'console.log')

When console.log("hello"); works perfectly fine in Safari.

When I use the JSC (JavaScriptCore) engine provided in the System Library, it acts differently then when using Safari's debug console

$ /System/Library/Frameworks/JavaScriptCore.framework/Versions/A/Resources/jsc
>>> console.log("hello");
Exception: TypeError: undefined is not an object (evaluating 'console.log')

When console.log("hello"); works perfectly fine in Safari.

• javascript
• safari
• javascriptcore

• 1 Because there's no console object in JSC, apparently. – Barmar Commented Jan 21, 2016 at 2:37
• @Barmar can you convert this to an answer so I can accept it? - Thanks – sdc Commented Jan 21, 2016 at 2:45
• I don't know anything about JSC, I just based that on the symptom. What's wrong with John Hascall's answer, that explains how to solve it? – Barmar Commented Jan 21, 2016 at 2:47
• @Barmar the problem has nothing to do with an Objective C or C environment but a JSC environment – sdc Commented Jan 21, 2016 at 3:04
• OK, I've reopened the question. You should put your solution in an answer, not the question. – Barmar Commented Jan 21, 2016 at 3:20

4 Answers 4

TL;DR

var Console = function () {
    this.log = function(msg){ debug(msg) }; 
};
var console = new Console();
console.log("hello");

Safari creates a console object that is available in the debug console, but not in the JSC environment. See Safari's console documentation here

Adding my own console object that wraps the JSC debug method solved my problem:

$ /System/Library/Frameworks/JavaScriptCore.framework/Versions/A/Resources/jsc
>>> var Console = function () {
...     this.log = function(msg){ debug(msg) };
... };
undefined
>>> var console = new Console();
undefined
>>> console.log("hello");
-> hello
undefined

The console object doesn't exist in JSC -- you can add it if you like JavaScriptCore console.log

I've ended up with this one liner that works on other JS engines along with JSC patibility:

console = console || { log: (...args) => debug(Array.prototype.slice.call(args).join(' ')) }

I learned from the answers above.

Though, as I not see a goal, I presume it was to see output on stdout:

print('string')

And when ready, use a stream editor to substitute 'print' with 'console.log'.