Math.PI - JavaScript 编辑

The Math.PI property represents the ratio of the circumference of a circle to its diameter, approximately 3.14159:

$$\mathtt{\mi{Math.PI}} = \pi \approx 3.14159$$

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The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

Property attributes of Math.PI
Writable	no
Enumerable	no
Configurable	no

Description

Because PI is a static property of Math, you always use it as Math.PI, rather than as a property of a Math object you created (Math is not a constructor).

Examples

Using Math.PI

The following function uses Math.PI to calculate the circumference of a circle with a passed radius.

function calculateCircumference(radius) {
  return Math.PI * (radius + radius);
}

calculateCircumference(1);  // 6.283185307179586

Specifications

Specification
ECMAScript (ECMA-262) The definition of 'Math.PI' in that specification.

Browser compatibility

BCD tables only load in the browser

See also

• Math