Javascript loop giving me problems

Question

I want to extract only groups from this string

I want to have something like in alert "group1,group2" but it returns empty.

var phone_nos = "group1,group2,564774890900"; 
var recipients = phone_nos.split(","); 
for( var i=0; i<recipients.length; i++ )
 group =recipients[i].substring(0,5)
{ if (group=="group")
 {groups.push(recipients)}
 }
 alert(groups.join(","))

• Waleed Khan: for (...) statement { block } is probably not doing what you expected it to do. Put the statement in the block.

Answer 1

Some misplaced braces for the for and assuming you want to filter group* you need to add recipients[i] the groups array rather than the original recipients string.

var phone_nos = "group1,group2,564774890900"; 
var recipients = phone_nos.split(","); 
var groups = [];
for (var i=0; i < recipients.length; i++) {
 group = recipients[i].substring(0,5);
 if (group == "group") {
 groups.push(recipients[i]);
 }
}
alert(groups.join(","))

Modern browsers/IE9+

var groups = phone_nos.split(",").filter(function(v) {
 return v.substring(0, 5) === "group"
});

Answer 2

You have an error of sorts.

for( var i=0; i<recipients.length; i++ ){
 group =recipients[i].substring(0,5)
 if (group=="group")
 {groups.push(recipients)}
}

You for statement was only running the next line of code, not the block I think. If you format your code better you will be better able to see errors like this.

for( var i=0; i<recipients.length; i++ )
 group =recipients[i].substring(0,5)
 // MORE CODE

This above only runs the first complete line after the for.