Javascript, increment a counter on button click

问题

In javascript, I want to make a counter that increases the value when you click a button.

When I click the add button the first time, the number doesn't increase.

But when I print the value to the console, the result increases.

The fiddle: http://jsfiddle.net/techydude/H63As/

  $(function() {
    var //valueCount = $("counter").value(),
        counter = $("#counter"),
        addBtn = $("#add"),
        value = $("#counter").html();

      addBtn.on("click", function() {

      counter.html(value ++);  //this value is not incremented.
      console.log(value);      //this value gets incremented.
      return

    });

  });

How do I make the value show the same for both lines?

回答1:

You are doing a Post Increment. Make it pre-increment:

addBtn.on("click", function() {
  counter.html(++value);
  console.log(value);
  return
});

Explanation:

// Increment operators
x = 1;
y = ++x;    // x is now 2, y is also 2
y = x++;    // x is now 3, y is 2

// Decrement operators
x = 3;
y = x--;    // x is now 2, y is 3
y = --x;    // x is now 1, y is also 1

回答2:

do you mean:

addBtn.on("click", function() {
    counter.html(++value);
    return;          
});

回答3:

use

 value = parseInt($("#counter").html());

LIVE jSFiddle

  $(function() {
    var //valueCount = $("counter").value(),
        counter = $("#counter"),
        addBtn = $("#add"),
        value =    parseInt($("#counter").html());


    addBtn.on("click", function() {

      counter.html(++value );
      console.log(value);
      return

    });

  });

回答4:

Try this:

  $(function() {
    var //valueCount = $("counter").value(),
        counter = $("#counter"),
        addBtn = $("#add"),
        value = $("#counter").html();


    addBtn.on("click", function() {

      counter.html(++value);
      console.log(value);
      return

    });

  });

Take a look in this link about the operator description of ++ in JavaScript.

Only one line actually changed; however, here is the fiddler link if you want to test it.

来源：https://stackoverflow.com/questions/13328717/javascript-increment-a-counter-on-button-click

标签

javascript

counter

increment