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CSS

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JavaScript

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HTML 

              
                <p>Practice removing Array elements using <span class="keyword">splice( <span class="start">start</span>, <span class="deleteCount">deleteCount</span> )</span>:</p>

<div id="ace"></div>

<div id="type"></div>

<!-- Add support for negative values: -1 [ ADDED ]-->
<!-- Add support for list.length -->
!

CSS 

              
                p {
  padding: 10px 20px;
  color: #bbb;
  font-size: 18px;
  font-family: Arial;
}
.keyword {
  font-weight: 600;
  color: #eee;
}
.start { color: green; }
.deleteCount { color: orange; }
body {
  background-color: black;
  margin: 0;
  padding: 0;
}
#ace {
  position: absolute;
  display: block;
  width: 100%;
  height: 15%;
}
#type {
  bottom:45%;
  position: absolute;
  display: block;
  width: 100%;
  height: 20%;
}
.ace_string {
  padding: 4px 6px;
  color: yellow !important;
  transition: all 500ms ease;
}
.ace_text-layer .ace_string.start {
  border-bottom: 5px solid green;
}
.ace_text-layer .ace_string.selected {
  background-color: orange;
  color:black !important;
}
.ace_text-layer .ace_string.count {
  background-color: hotpink;
  background-color: orange;
  color:black !important;
}
.myMarker {
  position:absolute;
  background: rgba(100,100,100,0.5) !important;
  z-index: 20;
}
.ace_line .ace_constant.ace_numeric:nth-child(5) {
  color: green !important;
}
.ace_line .ace_constant.ace_numeric:nth-child(7) {
  color: orange !important;
}
!

JS 

              
                let params = [];
let list = [ "item 1", "item 2", "item 3", "item 4" ];
let editor = ace.edit("ace");
editor.setBehavioursEnabled(true); 				
editor.setTheme("ace/theme/monokai");   editor.getSession().setMode("ace/mode/javascript");
editor.setShowPrintMargin(false);				
editor.$blockScrolling = Infinity;
editor.setValue('\nlet list = [ "item 1", "item 2", "item 3", "item 4"];', 1);
editor.setOptions({ fontSize: "12pt" });

let type = ace.edit("type");
type.setBehavioursEnabled(true); 				
type.setTheme("ace/theme/monokai");           
type.getSession().setMode("ace/mode/javascript");
type.setShowPrintMargin(false);				
type.$blockScrolling = Infinity;
type.setValue('// Syntax: splice( start, deleteCount ); \n// Practice by typing below and pressing Enter (only numbers are allowed):\nlist.splice( _, _ );', 1);
type.setOptions({ fontSize: "12pt" });
type.getSession().on('change', function(){ update() });
type.commands.addCommand({
  name    : "Return",
  exec    : function(){
    // Remove Elements
    list.splice( params[0], params[1] );
    console.log(params, list);
    editor.setValue('\nlet list = ' + JSON.stringify(list) + ';', 1);
  },
  bindKey : { mac: "enter", win: "enter" }
});

function update(){

  let val = type.getSession().getValue();
  let args = val.match(/\(\s?(-?\d)\s?,\s?(\d)\s?\)/);
  let items = document.querySelectorAll('.ace_string');
  let start = val.match(/\(\s?(-?\d)\s?,\s?.?\s?\)/);
  Array.from(items).map((item)=>item.classList.remove('start'));
  if ( start ){
    let idx = start[1] < 0 ? items.length + parseInt(start[1]) : start[1];
    if ( idx >= 0 ){
      items[idx] && items[idx].classList.add("start");
    }
  }
  if ( args ){
    params = [ args[1], args[2] ];
    let start = parseInt(args[1]);
    let idx = start < 0 ? items.length + parseInt(start) : start;
    let abs = idx;
    let deleteCount = parseInt(args[2]);
    if ( deleteCount > 0 ){
      items[idx].classList.add("selected");
    }
    while( deleteCount > 0 ){
  
      if ( idx == abs ){
        if ( items[idx] ){
          items[idx].classList.add("selected");
          idx++;
        }
      } else {
        if ( items[idx] ){
          items[idx].classList.add("count");
          idx++;
        }
      }
      deleteCount--;
    }
  } else {
    Array.from(items).map((item)=>{
      item.classList.remove('selected');
      item.classList.remove('count');
    });
  }
}
!
999px

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