JSTests/test262/test/built-ins/Number/prototype/toPrecision/undefined-precision-arg.js

// Copyright (C) 2016 The V8 Project authors. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.

/*---
esid: sec-number.prototype.toprecision
description: >
  Return a string containing the the number value of this if precision is
  undefined
info: |
  20.1.3 Properties of the Number Prototype Object

  The Number prototype object is the intrinsic object %NumberPrototype%. The
  Number prototype object is an ordinary object. The Number prototype is itself
  a Number object; it has a [[NumberData]] internal slot with the value +0.

  [...]
  The abstract operation thisNumberValue(value) performs the following steps:

  1. If Type(value) is Number, return value.
  2. If Type(value) is Object and value has a [[NumberData]] internal slot, then
    a. Assert: value's [[NumberData]] internal slot is a Number value.
    b. Return the value of value's [[NumberData]] internal slot.
  3. Throw a TypeError exception.

  Number.prototype.toPrecision ( precision )

  1. Let x be ? thisNumberValue(this value).
  2. If precision is undefined, return ! ToString(x).
  [...]
---*/

var n = new Number(7);

assert.sameValue(n.toPrecision(undefined), "7");
assert.sameValue((39).toPrecision(undefined), "39");

assert.sameValue(Number.prototype.toPrecision(), "0");
assert.sameValue((42).toPrecision(), "42");