aandrey,
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<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script>
window.addEventListener('DOMContentLoaded', function() {
[].forEach.call( document.querySelectorAll('.weight'), function(el) {
if (100 == +el.textContent) {
el = el.parentNode.previousElementSibling;
el && el.parentNode.removeChild(el)
}
});
});
</script>
</head>
<body>
<div id="help">
тут текст
</div>
<div id="number">
<span>Вес:</span><span class="weight">100</span>
</div>
<hr>
<div id="help">
тут проверка
</div>
<div id="number">
<span>Вес:</span><span class="weight">102</span>
</div>
</body>
</html>