拼接数组返回空结果

Question

I am trying to use splice top remove the last 2 items from an array. It always returns nothing. Trying to figure out what i am missing

 function planets_remove() { var planetsArray = []; planetsArray.push(document.getElementById("planets").value); var martian = planetsArray.splice(4,2)[0]; document.getElementById("planets_removed").innerHTML = martain; } 

 Enter 7 Planets<br> <textarea rows="5" cols="50" id="planets" name"planets"></textarea> <br><br> Click to remove the last 2 items from the array<br> <button type="button" class="processButton" onclick="planets_remove()">Remove</button><br> <p id="planets_removed"><p> <button type="button" class="processButton" onclick="planets_remove()">Remove</button><br> 

Answer 1

Try this Javascript code:

function planets_remove() {
  var planetsArray = document.getElementById("planets").value.split('\n');
  var martian = planetsArray.splice(0, planetsArray.length - 2);
  document.getElementById("planets_removed").innerHTML = martian;
}

The problem was, you were not pushing 7 elements, you were just pushing one multi-line string to an array.

You have to split the the string, so that it converts to individual elements. And then you can splice it.

Answer 2

Your array only ever contains one element (at most).

Solution: add a button to add new planet to the array after every input

Enter 7 Planets<br>
<textarea rows="5" cols="50" id="planets" name"planets"></textarea><br><br>
<button type="button" class="processButton" onclick="planets_add()"> Add </button><br>

Click to remove the last 2 items from the array<br>
<button type="button" class="processButton" onclick="planets_remove()"> Remove </button><br>
<p id="planets_removed"><p>

var planetsArray = [];
function planets_add() {
  planetsArray.push(document.getElementById("planets").value);
}

function planets_remove() {
  var martian = planetsArray.splice(4,2)[0];
  document.getElementById("planets_removed").innerHTML = martain;
}

Answer 3

You have to split textarea value by some splitter, here is example with space(' ').

 function planets_remove() { var planetsTxt = document.getElementById("planets"); var planetsArray = planetsTxt.value.split(' '); var martian = planetsArray.splice(planetsArray.length - 2, 2); document.getElementById("planets_removed").innerHTML = martian.join(' '); planetsTxt.value = planetsArray.join(' '); } 

 Enter 7 Planets<br> <textarea rows="5" cols="50" id="planets" name"planets"></textarea> <br><br> Click to remove the last 2 items from the array<br> <button type="button" class="processButton" onclick="planets_remove()">Remove</button><br> <p id="planets_removed"><p> <button type="button" class="processButton" onclick="planets_remove()">Remove</button><br>