Out of memory with running JavaScript by PhantomJS - shell

Question

My shell script is written in cygwin for windows:
// main.sh
#!/bin/bash
[ "$#" -lt 1 ] && echo "Usage: thisscript.sh <filename.txt>" && exit 0
filename=`basename -s .txt $1`
i=0
while [ $i == 0 ]
do
phantomjs --web-security=no myXHR.js $filename.txt
logLastLine=`tail -n 1 $filename.log`
if [[ "$logLastLine" =~ "Error" ]]; then
echo "Error occurs, now keep looping it..."
elseif [[ "$logLastLine" =~ "503" ]]; then
echo "Error occurs, now keep looping it..."
elseif [[ "$logLastLine" =~ "500" ]]; then
echo "Error occurs, now keep looping it..."
else
echo "Complete! Exiting the execution..."
i=1
fi
done
And here are the codes contained in the myXHR.js
// myXHR.js
phantom.onError = function(msg, trace) {
console.log("PhantomJS Error");
phantom.exit();
};
var fs = require('fs'), system = require('system');
if (system.args.length < 2) {
console.log("Usage: myXHR.js <FILE>");
}
var content = '',
f = null,
lines = null,
eol = "\n";
try {
f = fs.open(system.args[1], "r");
filename=system.args[1].replace(/\.txt/,"");
content = f.read();
} catch (e) {
console.log(e);
}
if (f) {
f.close();
}
var request = new XMLHttpRequest();
if (content) {
lines = content.split(eol);
for (i=0; i<(lines.length-1);i++) {
request.open('GET', "http://stackoverflow.com/", false);
request.send();
if （request.status === 200) {
try {
fs.write($filename.log, line[i] + "Succeed!", 'a');
} catch(e) {
console.log(e);
}
} else {
try {
fs.write($filename.log, line[i] + "Error!", 'a');
} catch(e) {
console.log(e);
}
}
}
phantom.exit();
To illustrate, the javascript, executed by PhantomJS, are reading 1st argument(a filename.txt file), passed into the shell script, line by line. For each line it sends a XMLHttpRequest to check the request status and writes it into filename.log file.
Error status number includes 503 and 500. Luckily these statuses are less likely to occur again if I resend the same XMLHttpRequest. So what I need to do is to set up a error handler which is for resend the same XMLHttpRequest when errors occur.
In this error handler, I use X=${tail -n 1 log} to see if there is a error status number(containing "503" or "500" string). For instance, if [[ "$X" =~ "503" ]]; then restart the execution of the javascript, by not giving i=1 and while loop never exits. Until it has finished reading the last line of the imported file without any error status numbers.
(I know it is awkward to handle error like this, but it was a quick solution that came to my mind.)
But this is theoretical. In practice, this script ended with an error "Memory exhausted". I reckon this error is triggered by the large amount of lines(>100k) in the $1 file, and it occurs in the JavaScript execution part. I used free -m command to get memory usage information, and I noticed that when Javascript is running, the used swap is increasing!
Could anybody teach me how to release the memory when the scripts is being executed.