如何遍历对象中的属性

Question

I want to iterate through an Object in a V8 C++ function.

NodeJS:

node.addProperties({"user":"testuser","password":"passwd"};

I want to pass "user" and "password", both names and values to a C++ method which takes parameters like:

AddProperty(char * name, char * value);

The number of name/value pairs may differ, so I need a generic solution.

Could I get some help to be put on the right track.

I have been writing simpler C++ wrappers for Node & V8, but I am just running out of ideas for this one :)

Answer 1

Assuming recent enough v8 (io.js or node 0.12), where the_object is the object passed from js

Local<Array> property_names = the_object->GetOwnPropertyNames();

for (int i = 0; i < property_names->Length(); ++i) {
    Local<Value> key = property_names->Get(i);
    Local<Value> value = the_object->Get(key);

    if (key->IsString() && value->IsString()) {
        String::Utf8Value utf8_key(key);
        String::Utf8Value utf8_value(value);
        AddProperty(*utf8_key, *utf8_value);
    } else {
        // Throw an error or something
    }
}

Answer 2

Since I just did this for my gem I might add some subtle changes to this answer by @Esailija which is now deprecated:

if (value->IsObject()) {
    Local<Context> context = Context::New(isolate);
    Local<Object> object = value->ToObject();
    MaybeLocal<Array> maybe_props = object->GetOwnPropertyNames(context);
    if (!maybe_props.IsEmpty()) {
        Local<Array> props = maybe_props.ToLocalChecked();
        for(uint32_t i=0; i < props->Length(); i++) {
           Local<Value> key = props->Get(i);
           Local<Value> value = object->Get(key);
           // do stuff with key / value
        }
    }

 }

The main addition is that

• You got to have a context going to get property names, the old way is getting deprecated
• You need to be careful when converting the value to an object

This works now, but as always be sure to check v8.h to get the latest non deprecated way.