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String interpolation is also known as string formatting. Advantages are:

1. code clarity

 "<li>" + "Hello " + name + ". You are visitor number" + visitor_num + "</li>";

is harder to read and edit than

Java/.Net way

String.Format("<li> Hello {0}. You are visitor number {1}. </li>", name, visitor_num);

python way

"<li> Hello %s. You are visitor number %s</li>" % (name, visitor_num)

javascript popular way

["<li>","Hello",name,". You are visitor number",visitor_num,"</li>"].join(',')

2. speed/memory use creating multiple strings and then concatenating them uses more memory and is slower than creating a single string one time.

I once wrote a javascript string formatter-

// simple string builder- usage: stringFormat("Hello {0}","world"); 
// returns "Hello world"
function stringFormat() {
 var s = arguments[0];
 for (var i = 0; i < arguments.length - 1; i++) {
 var reg = new RegExp("\\{" + i + "\\}", "gm");
 s = s.replace(reg, arguments[i + 1]);
 }
 return s;
};

String interpolation is also known as string formatting. Advantages are:

1. code clarity

 "<li>" + "Hello " + name + ". You are visitor number" + visitor_num + "</li>";

is harder to read and edit than

Java/.Net way

String.Format("<li> Hello {0}. You are visitor number {1}. </li>", name, visitor_num);

python way

"<li> Hello %s. You are visitor number %s</li>" % (name, visitor_num)

JavaScript popular way

["<li>","Hello",name,". You are visitor number",visitor_num,"</li>"].join('')

2. speed/memory use

Creating multiple strings and then concatenating them uses more memory and is slower than creating a single string one time.

I once wrote a javascript string formatter-

// simple string builder- usage: stringFormat("Hello {0}","world"); 
// returns "Hello world"
function stringFormat() {
 var s = arguments[0];
 for (var i = 0; i < arguments.length - 1; i++) {
 var reg = new RegExp("\\{" + i + "\\}", "gm");
 s = s.replace(reg, arguments[i + 1]);
 }
 return s;
}

String interpolation is also known as string formatting. Advantages are:

1. code clarity

 "<li>" + "Hello " + name + ". You are visitor number" + visitor_num + "</li>";

is harder to read and edit than

Java/.Net way

String.Format("<li> Hello {0}. You are visitor number {1}. </li>", name, visitor_num);

python way

"<li> Hello %s. You are visitor number %s</li>" % (name, visitor_num)

javascript popular way

["<li>","Hello",name,". You are visitor number",visitor_num,"</li>"].join(',')

2. speed/memory use creating multiple strings and then concatenating them uses more memory and is slower than creating a single string one time.

I once wrote a Java/.Net style string formatter for javascript, so since you asked specifically about javascript, here it is-

// simple string builder- usage: stringFormat("Hello {0}","world"); 
// returns "Hello world"
function stringFormat() {
 var s = arguments[0];
 for (var i = 0; i < arguments.length - 1; i++) { 
 var reg = new RegExp("\\{" + i + "\\}", "gm"); 
 s = s.replace(reg, arguments[i + 1]);
 }
 return s;
};

String interpolation is also known as string formatting. Advantages are:

1. code clarity

 "<li>" + "Hello " + name + ". You are visitor number" + visitor_num + "</li>";

is harder to read and edit than

Java/.Net way

String.Format("<li> Hello {0}. You are visitor number {1}. </li>", name, visitor_num);

python way

"<li> Hello %s. You are visitor number %s</li>" % (name, visitor_num)

javascript popular way

["<li>","Hello",name,". You are visitor number",visitor_num,"</li>"].join(',')

2. speed/memory use creating multiple strings and then concatenating them uses more memory and is slower than creating a single string one time.

I once wrote a javascript string formatter-

// simple string builder- usage: stringFormat("Hello {0}","world"); 
// returns "Hello world"
function stringFormat() {
 var s = arguments[0];
 for (var i = 0; i < arguments.length - 1; i++) { 
 var reg = new RegExp("\\{" + i + "\\}", "gm"); 
 s = s.replace(reg, arguments[i + 1]);
 }
 return s;
};