var yourImages = [
["assets/proj-1/proj_1.gif","assets/proj-1/proj_2.gif"],
["assets/proj-1/proj_3.gif","assets/proj-1/proj_4.gif"],
["assets/proj-1/proj_5.gif","assets/proj-1/proj_6.gif"],
["assets/proj-1/proj_7.gif","assets/proj-1/proj_8.gif"],
["assets/proj-1/proj_9.gif","assets/proj-1/proj_10.gif"],
["assets/proj-1/proj_11.gif","assets/proj-1/proj_12.gif"],
["assets/proj-1/proj_13.gif","assets/proj-1/proj_14.gif"],
["assets/proj-1/proj_15.gif","assets/proj-1/proj_16.gif"],
["assets/proj-1/proj_17.gif","assets/proj-1/proj_18.gif"],
["assets/proj-1/proj_19.gif","assets/proj-1/proj_20.gif"],
["assets/proj-1/proj_21.gif"]
]

preloadImages=[]

for(var i=0;i<yourImages.length;i++){
preloadImages[i]=[]

for(var j=0;j<yourImages[i].length;j++){
preloadImages[i][j]=new Image()
preloadImages[i][j].src=yourImages[i][j]
}

}