In computer programming, a block or code block is a section of code which is grouped together. Blocks consist of one or more declarations and statements. A programming language that permits the creation of blocks, including blocks nested within other blocks, is called a block-structured programming language. JavaScript is one such programming language.

A block statement in JavaScript is used to group zero or more statements. The block is delimited by a pair of curly brackets.

{
  statement_1;
  statement_2;
  ...
  statement_n;
}

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The block statement is commonly used with control flow statements (e.g. if...else, for, while) and functions.

while (x < 10) {
  x++;
}

function addnums(num1, num2) {
  var sum = 0;
  sum = num1 + num2;
  return sum;
}