How can I change the default behavior of console.log in Safari?

问题

In Safari with no add-ons, console.log will show the object at the last state of execution, not at the state when console.log was called.

I have to clone the object just to output it via console.log to get the state of the object at that line.

Example:

var test = {a: true}
console.log(test); // {a: false}
test.a = false; 
console.log(test); // {a: false}

回答1:

I think you're looking for console.dir().

console.log() doesn't do what you want because it prints a reference to the object, and by the time you pop it open, it's changed. console.dir prints a directory of the properties in the object at the time you call it.

The JSON idea below is a good one; you could even go on to parse the JSON string and get a browsable object like what .dir() would give you:

console.log(JSON.parse(JSON.stringify(obj)));

回答2:

What I usually do if I want to see it's state at the time it was logged is I just convert it to a JSON string.

console.log(JSON.stringify(a));

回答3:

Vanilla JS:

@evan's answer seems best here. Just (ab)use JSON.parse/stringify to effectively make a copy of the object.

console.log(JSON.parse(JSON.stringify(test)));

JQuery specific solution:

You can create a snapshot of an object at a certain point in time with jQuery.extend

console.log($.extend({}, test));

What is actually happening here is jQuery is creating a new object with the test object's content, and logging that (so it will not change).

AngularJS (1) specific solution:

Angular provides a copy function that can be used to the same effect: angular.copy

console.log(angular.copy(test));

Vanilla JS wrapper function:

Here is an function which wraps console.log but will make a copy of any objects before logging them out.

I wrote this in response to a few similar but less robust functions in the answers. It supports multiple arguments, and will not try to copy things if they are not regular objects.

function consoleLogWithObjectCopy () {
  var args = [].slice.call(arguments);
  var argsWithObjectCopies = args.map(copyIfRegularObject)
  return console.log.apply(console, argsWithObjectCopies)
}

function copyIfRegularObject (o) {
  const isRegularObject = typeof o === 'object' && !(o instanceof RegExp)
  return isRegularObject ? copyObject(o) : o
}

function copyObject (o) {
  return JSON.parse(JSON.stringify(o))
}

example usage: consoleLogWithObjectCopy('obj', {foo: 'bar'}, 1, /abc/, {a: 1})

回答4:

That > Object in the console, isn't only showing the current state. It actually is deferring reading the object and it's properties until you expand it.

For example,

var test = {a: true}
console.log(test);
setTimeout(function () {
    test.a = false; 
    console.log(test);
}, 4000);

Then expand the first call, it will be correct, if you do it before the second console.log returns

回答5:

using Xeon06's hint, you may parse his JSON in an object, and here is the log function I now use to dump my objects :

function odump(o){
   console.log($.parseJSON(JSON.stringify(o)));
}

回答6:

I defined an utility:

function MyLog(text) {
    console.log(JSON.stringify(text));
}

and when I want to log on console I simply do:

MyLog("hello console!");

It works very well!

回答7:

You might want to log the object in a human readable way:

console.log(JSON.stringify(myObject, null, 2));

This indents the object with 2 spaces at each level.

How can I pretty-print JSON using JavaScript?

回答8:

There is an option to use a debugger library.

https://debugjs.net/

Just include the script into your web page and put log statements.

<script src="debug.js"></script>

Logging

var test = {a: true}
log(test); // {a: true}
test.a = false; 
log(test); // {a: false}

回答9:

I may be shot for suggesting this, but this can be taken one step further. We can directly extend the console object itself to make it more clear.

console.logObject = function(o) {
  (JSON.stringify(o));
}

I don't know if this will cause some type of library collision/nuclear meltdown/rip in the spacetime continuum. But it works beautifully in my qUnit tests. :)