How to load JSON models first in three.js and assign a variable before init?

I want to load quite a lot of JSON models and put them in global variables so I can use them to copy, translate, etc. That way I won't have to load a model every time i need one.

I tried some methods but it seems loading the models happens asynchronously.

The models seem to be loaded after everything else is already done. So I will already have declared my variables but they stay empty or don’t work. How do I load the models first, wait until that is done and then start the init() and the rest of my code?

example:

var loader = new THREE.JSONLoader();

var test1 = new THREE.Object3D();
var test2 = new THREE.Object3D();
var test3 = new THREE.Object3D();
var test4 = new THREE.Object3D();
var test5 = new THREE.Object3D();
var test6 = new THREE.Object3D();
var test7 = new THREE.Object3D();

loadparts();
init();
animate();

function init() {
    var newpart = test1.clone();
    console.log("newpart.id:" + newpart.id);
    newpart.position.set(0,0,0);
    scene.add(newpart);

    console.log("test1.children.length:" + test1.children.length);

    placePart(test1,0,100,0);
    placePart(test2,0,200,0);
    placePart(test3,0,300,0);
    placePart(test4,0,400,0);
    placePart(test5,0,500,0);
    placePart(test6,0,600,0);
    placePart(test7,0,700,0);
}

function loadparts( ) {

    loader.load( "Models/test1.js", function ( geometry, materials ) { createPart( geometry, materials, test1 ) } );
    loader.load( "Models/test2.js", function ( geometry, materials ) { createPart( geometry, materials, test2 ) } );
    loader.load( "Models/test3.js", function ( geometry, materials ) { createPart( geometry, materials, test3 ) } );
    loader.load( "Models/test4.js", function ( geometry, materials ) { createPart( geometry, materials, test4 ) } );
    loader.load( "Models/test5.js", function ( geometry, materials ) { createPart( geometry, materials, test5 ) } );
    loader.load( "Models/test6.js", function ( geometry, materials ) { createPart( geometry, materials, test6 ) } );
    loader.load( "Models/test7.js", function ( geometry, materials ) { createPart( geometry, materials, test7 ) } );
}

function createPart( geometry, materials, object3Dtemp) {
    Part = new THREE.Mesh( geometry, new THREE.MeshFaceMaterial( materials ) );
    Part.scale.set( 1000, 1000, 1000 );
    console.log("ModelPart created:" + Part.id);
    object3Dtemp.add( Part );
}

function placePart( object3Dtemp, x, y, z) {
    Part = object3Dtemp.clone();
    Part.position.set( x, y, z );

    console.log("Part.id:" + Part.id);
    scene.add( Part );
}

in console:

newpart.id:12 
test1.children.length:0
Part placed: 0 100 0 13 
Part placed: 0 200 0 14 
Part placed: 0 300 0 15 
Part placed: 0 400 0 16 
Part placed: 0 500 0 17 
Part placed: 0 600 0 18 
Part placed: 0 700 0 19
THREE.WebGLRenderer 63 
ModelPart created:21 
ModelPart created:22 
ModelPart created:23 
ModelPart created:24 
ModelPart created:25 
ModelPart created:26 
ModelPart created:27