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String

A string is basically a sequence of characters. A string variable can be declared with a string literal or the String object.

A string literal is enclosed within "...", '...', or `...`. The first two forms are interchangeable. They can span multiples by using a \ at the end of lines.

ECMAScript 6 introduces the third form of strings, template literals, which are enclosed within `...`. They can interpolate expressions within. They can also span multiple lines.


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<!DOCTYPE html><html><body><script>


   var a='123'; console.log(a); // 123
   var b="a'b'c"; console.log(b); // a'b'c
   var c=`${a}`; console.log(c); // 123
   var c=`${a+b}`; console.log(c); // 123a'b'c
   console.log("hello \
                     world"); // hello
                 world
   console.log(`hello
                      world`);  // hello                                     //
          world
   console.log(`${3+4}-eleven`);  // 7-eleven

</script></body><html>

A template string can be passed to a function without the parentheses, as a tagged template string.


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<!DOCTYPE html><html><body><script>

function f(strings, ...values) {
  console.log(strings[0]); // a
  console.log(strings[1]); // bc
  console.log(strings[2]); // d
  console.log(values[0]);  // 42
  console.log(values[1]);  // 999}f `a${ 42 }bc${999}d`;

</script></body><html>

To silence errors caused by invalid Unicode escape sequence, enclose the Unicode within {}.


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<!DOCTYPE html><html><body><script>

console.log("\u9999");   // 香//console.log("\u55");   // SyntaxError: Invalid Unicode console.log("\u{55}");   // U: no error if tagged with {}function tag(s){
    console.log(s[0]);      // undefined
    console.log(s[1]);      // undefined
    console.log(s.raw[0]);  // \u55 \u{55}}tag `\u55 \u{55}`;

</script></body><html>

Note that a string is also an iterable.