[JavaScript] Deep Copy in JavaScript

Thu, 08 Dec 2016 09:42:07 +0000

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var obj1 = JSON.parse(JSON.stringify(obj2));

The above method uses JSON round-trip conversion for deep copying arrays or objects. It has some limitations but works for most cases. For details, see
https://segmentfault.com/a/1190000000501320

Counting Valid Lines in a Textarea with JavaScript

Thu, 19 Mar 2015 12:30:42 +0000

I recently had a requirement to count the number of valid (non-empty) lines in a textarea on a page, limit the total number of lines, and display the remaining available lines. [Besides counting lines, you could also check for spaces, commas, semicolons, etc. – the approach is similar.]

My initial idea was: Write a regex to replace multiple consecutive newlines “\n” with a single “\n”: str.replace(/\n+/, "\n"); But this doesn’t handle cases where there are multiple empty lines with leading spaces.

Later: Simply split by “\n”, then count entries with length greater than 0 as valid lines.

Here’s the code:

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<script type="text/javascript">
var maxTagCount = 100;
function checkLine(textArea) {
 var str = textArea.value;
 var lines = str.split('\n');
 var countLine = 0;
 for (var i = 0; i < lines.length; i++) {
 if (lines[i].length > 0) {
 countLine++;
 }
 }
 var tagElement = document.getElementById("tagTextarea");

 if (countLine > maxTagCount) {
 var varNewValue = "";
 var index = 0;
 for (var i = 0; i < lines.length; i++) {
 if (index >= maxTagCount) {
 break;
 }
 if (lines[i].length > 0) {
 index++;
 }
 varNewValue += lines[i];
 varNewValue += "\n";
 }
 textArea.value = varNewValue;
 stat_left.innerHTML = 0;
 } else {
 stat_left.innerHTML = maxTagCount - countLine;
 }
}
</script>

JavaScript on Coinidea's Blog

[JavaScript] Deep Copy in JavaScript

Counting Valid Lines in a Textarea with JavaScript

Web demo: countLines