Chrome JavaScript developer console: Is it possible to call console.log() without a newline?

Question

I'd like to use console.log() to log messages without appending a new line after each call to console.log(). Is this possible?

Solution 1

No, it's not possible. You'll have to keep a string and concatenate if you want it all in one line, or put your output elsewhere (say, another window).

Solution 2

In NodeJS you can use process.stdout.write and you can add '\n' if you want.

console.log(msg) is equivalent to process.stdout.write(msg + '\n').

Solution 3

Yes, it's possible (check out the demo below) -- by implementing your own virtual console on top of the native browser console, then syncing it to the real one.

This is much easier than it sounds:

1. maintain a display buffer (e.g. an array of strings representing one line each)
2. call console.clear() before writing to erase any previous contents
3. call console.log() (or warn, error, etc) to fill the console with the contents from your display buffer

Actually, I've been doing this for some time now. A short, rudimentary implementation of the idea would be something along the following lines, but still capable of animating the console contents:

// =================================================
// Rudimentary implementation of a virtual console.
// =================================================

var virtualConsole = {
    lines: [],
    currentLine: 0,
    log: function (msg, appendToCurrentLine) {
        if (!appendToCurrentLine) virtualConsole.currentLine++;
      
        if (appendToCurrentLine && virtualConsole.lines[virtualConsole.currentLine]) {
            virtualConsole.lines[virtualConsole.currentLine] += msg;
        } else {
            virtualConsole.lines[virtualConsole.currentLine] = msg;
        }
        
        console.clear();
        
        virtualConsole.lines.forEach(function (line) {
            console.log(line);
        });
    },
    clear: function () {
        console.clear();
        virtualConsole.currentLine = 0;
    }
}

// =================================================
// Little demo to demonstrate how it looks.
// =================================================

// Write an initial console entry.
virtualConsole.log("Loading");

// Append to last line a few times.
var loadIndicatorInterval = setInterval(function () {
    virtualConsole.log(".", true); // <- Append.
}, 500);

// Write a new line.
setTimeout(function () {
    clearInterval(loadIndicatorInterval);
    virtualConsole.log("Finished."); // <- New line.
}, 8000);

It sure has its drawbacks when mixing with direct console interaction, and can definitely look ugly -- but it certainly has its valid uses, which you couldn't achieve without it.

Solution 4

You can put as many things in arguments as you'd like:

console.log('hi','these','words','will','be','separated','by','spaces',window,document)

You'll get all that output on one line with the object references inline and you can then drop down their inspectors from there.

Solution 5

The short answer is no.

But

If your use-case involves attempting to log perpetually changing data while avoiding console-bloat, then one way to achieve this (in certain browsers) would be to use console.clear() before each output.

function writeSingleLine (msg) {

  console.clear();
  console.log(msg);

}

writeSingleLine('this');
setTimeout( function () { writeSingleLine('is'); }, 1000);
setTimeout( function () { writeSingleLine('a'); }, 2000);
setTimeout( function () { writeSingleLine('hack'); }, 3000);

Note that this would probably break any other logging functionality that was taking place within your application.

Disclaimer: I would class this as a hack.

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Comments

[newenglander]

Was one of the answers correct?

[Dave Land]

I think @minitech's answer is correct: it is not possible. The other answers provide interesting, if somewhat orthogonal depth to our understanding of console.log().

[John Weisz]

@DaveLand I believe it is perfectly possible by maintaining your own display buffer, and syncing that display buffer to the actual console by a combination of console.clear() and, e.g. console.log().

[Dave Land]

@JohnWeisz: Thanks, but wiping the entire console for every "inline" update is not a solution for about 99% of applications. Still, have an updoot.

[John Weisz]

@DaveLand Yeah, it's more like a hack -- and now that I looked around, I realized it has been proposed before. Either way, it can be useful at times.

[Dave Land]

@JohnWeisz Useful for monitoring an ongoing process, using the console as a progress bar, provided that no other useful info appears in the log :-).

[JohnAllen]

How does this answer the question?

[Admin]

I think this answer is useful.

[Sean Lynch]

This is useful. Even though it doesn't answer the question, it does provide a solution to what most people would be looking for when they find this question.

[Karl Adler]

The reason why any would like to print without new line is that the following output is not known. Or just imagine a "loader bar" using e.g. dots.

[vp_arth]

A.forEach(row => console.log(row.join(' ')))

[danShumway]

Very much a hack, but clever. If you tracked what's already been logged to the console (say by maintaining some kind of virtual buffer), you could rebuild the buffer and append a new string every time you cleared.

[deltaray]

Actually, it is possible, but maybe not for the use everyone has in mind. In my case, I was just trying to print a question to get input from a command line terminal. See the answer to this question for the answer: stackoverflow.com/questions/26683734/…

[Ry-]

@deltaray readline’s question is not console.log. The question is also about the browser console, not Node.js.

[Alex]

NodeJS is not Chrome. This answer is irrelevant to the question 'can you console.log without a newline?'.

[Qwerty]

Using multiple arguments breaks console.log styling as you can only style within first argument.

[imran khan]

@minitech you can use spread operator to print in one line. see in example jsfiddle.net/imranqau5373/7m65at9L/2

[Ry-]

@imrankhan: That’s not what the question was. The spread operator doesn’t add anything new here vs. passing multiple arguments/using apply.

[Matt Way]

This is the best answer here. You can even init with say max lines that keeps the log stack sufficiently short, so that you don't end up logging a huge set of data.

[AbdurRehman Khan]

This answer is indeed useful.

[Pablo Yabo]

I landed here looking for this, so it was good to add the solution. Others think the same.

[stone]

Upvoted for actually answering the question! The answer is NO.