JSON Testing

Test if input is valid JSON.

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.0.0-rc1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.13.1/lodash.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/autosize.js/3.0.15/autosize.min.js"></script>
<div id="output">Ready</div>
<div class="wrapper">
  <textarea name="json-input" id="json-input" class="form-input" type="text" placeholder='{"enter": "json"}' rows="1" autofocus></textarea>
</div>

CSS

.wrapper {
  margin: 15px;
  font-family: 'Arial', sans-serif;
  font-size: 14px;
  background: #f9f9f9;
  padding: 5px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, .05),
              inset 0 1px 0 rgba(255,255,255,1);
  border-radius: 2px;
  border: 1px solid #d3d3d3;
}

#output {
  background: rgba(255, 255, 255, .95);
  bottom: 15px;
  right: 15px;
  position: fixed;
  padding: 6px 12px 5px 12px;
  font-family: 'Calibri', sans-serif;
  font-size: 16px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, .05);
  border-radius: 2px;
  border: 1px solid #d3d3d3;
  text-shadow: 0 1px 0 rgba(255, 255, 255, .015);
}

#invalid-text {
  color: #A00;
}

#valid-text {
  color: #0A0;
}

.form-input {
  height: 16px;
  overflow: hidden;
  resize: vertical;
  box-sizing: border-box;
  display: block;
  width: 100%;
  font-size: 16px;
  font-family: 'Courier New', monospace;
  outline: none !important;
  padding: 6px 12px;
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, .10);
  border: 1px solid #d3d3d3;
  text-shadow: 0 1px 0 rgba(255, 255, 255, .015);
}

JavaScript

function isJSON(json) {
  try {
    var obj = JSON.parse(json)
    if (obj && typeof obj === 'object' && obj !== null) {
      return true
    }
  } catch (err) {}
  return false
}

$(function() {
  var $output = $('#output')
  	, $input = $('#json-input')
  autosize($input)
  $input.on('keyup', function() {
    var $this = $(this),
      $val = $this.val()
    if ($val.length >= 1) {
      $output.html((isJSON($val)
        ? '<span id="valid-text">VALID</span>'
        : '<span id="invalid-text">INVALID</span>'))
        .show()
    } else {
      $output.hide()
    }
  });
})