将key：value复制到数组Javascript的对象元素中

Question

This is a simple test of javascript knowledge that I seem to be lacking. I'm basically writing a query front end for monogdb, it's almost done apart from one little piece. Queries are built by clicking elements and most of the logic works. I'm stuck on building an $and query.

I have a flat object like this:

obj1: {
    prop1: 'val1'
}

These key values are added dynamically when the user clicks on a list-item and enters a custom value. When the user clicks 2 or more items from the list-items I would like for my object to end up like this:

obj1: {
  $and: [
  {prop1: 'val1'},
  {prop2: 'val2'},
  {prop3: 'val3'}
  ]
}

Where all the original key value strings are wrapped in {} and become elements to an $and array.

I can get the first part working ie turning the key values into objects. And I can get the second part, injecting an $and array and feeding it some kind of object but I can't get the two to work together consistently.

It requires taking the value already in obj1 , making an object out of it and pushing it into an array. Injecting that array into obj1 , and then removing the old key value from obj1 .

This is as far as I've got:

var add = []
var newElementObject= {}

for (var prop in obj1) {
    newElementObject = {};
    newElementObject[prop] = "custom value entered by user";
    delete obj1[prop]
    add.push(newElementObject);
}

obj1.$and = add;

It works, once. I get the structure I'm looking for but when I try to add more items to the $and array something craps out. The second obj updates and the first just sits there saying:

{$and : "custom value entered by user"}

I've been staring at this for too long.

Answer 1

Try

var newElementObject = {};
obj1.$add = obj1.$add || []; //keep the old array or make a new one

for (var prop in obj1) {
    if (!obj1.hasOwnProperty(prop) || prop == '$add') { continue; }
    newElementObject = {};
    newElementObject[prop] = "custom value entered by user";
    delete obj1[prop]
    obj1.$add.push(newElementObject);
}

That way you're not going to overwrite the old array reference if you run this code twice on the same object, which is what it sounds like your problem is.