javascript animation effect time interval -

there falling word, , store positions(x,y) , value separate arrays, , if type specific word, remove values in 3 arrays.

i set interval time 800, problem deletion of word corresponds interval time rather deletes following word.

i think because draw() function under update, under influence of interval time, i'm not sure how maintain draw of contents , erase after made input.

var intervaltime = 800;    setinterval(update, intervaltime); //appearance interval  function dokey (keypressed) {     if (window.event.keycode === 13) { //if pressed enter         var submission = document.getelementbyid('inputbox').value;         var result = checkletter(submission);         if (result > -1) {             //value deletion             alpha.splice(result, 1);             //positions deletion             listx.splice(result, 1);             listy.splice(result, 1);             increasescore('score');         } else {             console.log("this error");         }     document.getelementbyid('inputbox').value = ''; //return first step     } }  function draw() {     (i = 0; < alpha.length; i++) {         listy[i] += spdy;         ctx.filltext(alpha[i],listx[i],listy[i]);     } }  function update() {     if (document.getelementbyid('life').innerhtml == 0) {         alpha = []         listx = []         listy = []         console.log("fail");         endofthegame();     } else {         increaselevel();         //console.log(alpha);         //console.log(listx);         //console.log(listy);         spdy = 50 + 5*(document.getelementbyid('score').innerhtml/10);//speed         lifededuction()         getletter();         ctx.clearrect(0,0,500,500);         draw();     } } 

you can call draw() function dokey() function ctx.clearrect(0,0,500,500); called before redraw screen. way screen updates other parts of update() function not execute.