javascript - V8: console.log implementation - Stack Overflow

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I'm using V8 in my C++ app and I would like to add console.log(). Is there some good standard implementation I can use?

Currently, I have my own dummy implementation but it's quite inplete.

I'm using V8 in my C++ app and I would like to add console.log(). Is there some good standard implementation I can use?

Currently, I have my own dummy implementation but it's quite inplete.

• javascript
• v8

Share Improve this question Follow asked Mar 10, 2014 at 11:07 AlbertAlbert 68.4k6868 gold badges252252 silver badges403403 bronze badges

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1 Answer 1

Sorted by: Reset to default 7

I just found this implementation from Node.js:

https://github./joyent/node/blob/master/lib/console.js https://github./joyent/node/blob/master/lib/util.js

Of course you need to adopt this code. It uses the Nodejs global object process and its stdout and stderr objects. Here is some sample C++ code to create such file objects:

static void js_file_write(const v8::FunctionCallbackInfo<v8::Value>& info) {
    int fd = (int) info.Data().As<External>()->Value();
    auto isolate = Isolate::GetCurrent();
    if( info.Length() != 1) {
        isolate->ThrowException(
            v8::Exception::TypeError(jsStr("js_file_write: expects exactly 1 arg")));
        return;
    }
    if( !info[0]->IsString() ) {
        isolate->ThrowException(
            v8::Exception::TypeError(jsStr("js_file_write: expects a string")));
        return;
    }
    std::string s = jsObjToString(info[0], false, "");
    size_t c = 0;
    while(c < s.size()) {
        int ret = write(fd, &s[c], (unsigned int) (s.size() - c));
        if(ret < 0) {
            isolate->ThrowException(
                v8::Exception::Error(jsStr("js_file_write: write(" + to_string(fd) + ") error " + to_string(errno) + ": " + strerror(errno))));
            errno = 0;
            return;
        }
        c += ret;
    }
}


static Local<Object> makeFileObj(int fd) {
    auto isolate = Isolate::GetCurrent();
    Handle<External> selfRef = External::New(isolate, (void*) fd);
    auto obj = Object::New(isolate);
    obj->Set(jsStr("write"),
        FunctionTemplate::New(isolate, js_file_write, selfRef)->GetFunction());
    return obj;
}

static Local<Object> makeProcessObj() {
    auto obj = Object::New(Isolate::GetCurrent());
    obj->Set(jsStr("stdout"), makeFileObj(STDOUT_FILENO));
    obj->Set(jsStr("stderr"), makeFileObj(STDERR_FILENO));
    return obj;
}

jsStr and jsObjToString are quite canonical.

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