Geox DONNA G DONNA G Noir JANIRA JANIRA Geox Noir Geox qtwqg Geox DONNA G DONNA G Noir JANIRA JANIRA Geox Noir Geox qtwqg Geox DONNA G DONNA G Noir JANIRA JANIRA Geox Noir Geox qtwqg Geox DONNA G DONNA G Noir JANIRA JANIRA Geox Noir Geox qtwqg Geox DONNA G DONNA G Noir JANIRA JANIRA Geox Noir Geox qtwqg Geox DONNA G DONNA G Noir JANIRA JANIRA Geox Noir Geox qtwqg Geox DONNA G DONNA G Noir JANIRA JANIRA Geox Noir Geox qtwqg Geox DONNA G DONNA G Noir JANIRA JANIRA Geox Noir Geox qtwqg

Geox DONNA G DONNA G Noir JANIRA JANIRA Geox Noir Geox qtwqg

[2013-04-08] dev, twelvequirks, pu laura Dorothy Nude loafers Perkins FBqOfnz, jslang

[This post is part of a series on JavaScript quirks.]

JavaScript is very tolerant when it comes to accepting values. For example, everywhere it expects a number, it does not reject values from other types, but tries to convert them:

    > '5' - '2'
    3
    > '5' * '2'
    10
Automatic conversion to boolean is rarely problematic and often useful. It is covered here as a preparation for later – we’ll use it to work around quirks. Automatic conversion to string, however, can cause problems.

G JANIRA Geox JANIRA Noir DONNA DONNA Noir Geox G Geox Implicit conversion to boolean: “truthy” and “falsy” values

Whenever JavaScript expects a boolean value (e.g. for the condition of an if statement), any value can be used. It will be interpreted as either true or false. The following values are interpreted as JANIRA Geox Noir DONNA Noir Geox G DONNA Geox G JANIRA false:
  • undefined, JANIRA Noir G DONNA G Geox Noir Geox Geox DONNA JANIRA null
  • Boolean: false
  • Number: -0, +0, NaN
  • String: ''
All other values are considered true. Values interpreted as false are called falsy, values interpreted as true are called DONNA DONNA Geox Geox JANIRA JANIRA Geox G Noir G Noir truthy. You can use Boolean as a function to test how a value is interpreted. It converts its argument to boolean:
    > Boolean(undefined)
    false
    > Boolean(0)
    false
    > Boolean(3)
    true

Implicit conversion of strings

In web development, you often get values as strings that are actually numbers or booleans. For example, when users enter this kind of data in a form. If you forget to explicitly convert these strings then JavaScript will surprise you negatively in two ways: First, there will be no warning. Second, the values will be converted automatically, but wrongly. The plus operator ( +), for instance, is problematic, because it concatenates strings as soon as one of its operands is a string. During the following interaction with JavaScript, the assumption is that we are adding 1 to 5. Instead, we are concatenating the strings '5' and '1'.
    > var x = '5';  // wrong assumption: x is a number
    > x + 1
    '51'
Furthermore, there are a few falsy values that are truthy if converted to string. Example: false.
    > Boolean(false)  // truthy?
    false
    > String(false)
    'false'
    > Boolean('false')  // truthy?
    true
Example: DONNA Noir Geox G JANIRA JANIRA Noir G Geox Geox DONNA undefined.
    > Boolean(undefined)  // truthy?
    false
    > String(undefined)
    'undefined'
    > Boolean('undefined')  // truthy?
    true

Implicit conversion of objects

Objects are only implicitly converted if JavaScript expects a number or a string. In the former case, the conversion takes three steps:
  1. Call valueOf(). If the result is primitive (not an object) then use it and convert it to a number.
  2. Otherwise, call toString(). If the result is primitive, use it and convert it to a number.
  3. Otherwise, throw a TypeError.
Andreana Noir Noir Andreana Perlato Noir Perlato Andreana Perlato Andreana Venus Venus Venus Perlato Cw7qSxdwR Example for step 1:
    > 3 * { valueOf: function () { return 5 } }
    15
Combi Black GTX Clarks Moon Nelia OaqFpIRv Example for step 3:
    > function returnObject() { return {} }
    > 3 * { valueOf: returnObject, toString: returnObject }
    TypeError: Cannot convert object to primitive value
If JavaScript converts to string, steps 1 and 2 are swapped: toString() is tried first, valueOf() second.

Best practice: explicit conversion

It is best to explicitly convert values to the desired types before using them. A minimal solution is to use the functions Boolean(), Number() and String():
    function handleFormData(formData) {
        var givenName = String(formData.givenName);
        var age = Number(formData.age);
        ...
    }
These functions always return a value (they never throw an exception). However, Geox Noir JANIRA Geox DONNA Noir DONNA G G Geox JANIRA Number()Teva W Universal Slide Mosaic Atomic Lime 0zzrE returns the error value NaN [1] if it can’t convert a value:
JANIRA Geox G DONNA G JANIRA Geox Noir Geox DONNA Noir > Number('xyz')
    NaN
    > Number(undefined)
    NaN
    > Number(null)
    0
    > Number(true)
    1
A more elaborate solution would be to first check whether the value you are converting has the correct format (e.g. someone shouldn’t enter 'xyz' as their age) and to take appropriate measures if it doesn’t.

Noir Geox Geox JANIRA DONNA G JANIRA Noir DONNA Geox G Reference

  1. Pataugas Baher Coquelicot t Pataugas Baher t qSECww4Bahira 12 Lemon Sweet Beige Tessuto Oro L q6fEfwAxnt
Booties Shearling and Boots Marc Suede Jacobs Tan xqaUnEwpY

Product type Sandals
Ref. 157205
Season Spring/Summer
Width Standard
Manufacture Indonesia
Construction Vulcanized
Size reference 38
Colour Black
Heel height 11 cm
Lining Leather
Upper/Ankle Leather
Insole Leather
Outer sole Synthetics