_.function.predicates.js.md

function.predicates

Functions which return whether the input meets a condition.

isAssociative

Signature: isAssociative(value:Any)

Returns a boolean indicating whether or not the value is an associative object. An associative object is one where its elements can be accessed via a key or index (e.g. arrays, arguments, objects).

_.isAssociative(["Athens", "Sparta"]);
// => true

_.isAssociative(42);
// => false

isDecreasing

Signature: _.isDecreasing(values:Any...)

Checks whether the arguments are monotonically decreasing values (i.e. whether each argument is less than the previous argument.)

_.isDecreasing(3, 2, 1);
// => true

_.isDecreasing(15, 12, 2);
// => true

_.isDecreasing(2, 3);
// => false

isEven

Signature: _.isEven(value:Any)

Checks whether the value is an even number.

_.isEven(12);
// => true

_.isEven(3);
// => false

_.isEven({});
// => false

isFloat

Signature: _.isFloat(value:Any)

Checks whether the value is a “float.” For the purposes of this function, a float is a numeric value that is not an integer. A numeric value may be a number, a string containing a number, a Number object, etc.

NOTE: JavaScript itself makes no distinction between integers and floats. For the purposes of this function both 1 and 1.0 are considered integers.

_.isFloat(1.1);
// => true

_.isFloat(1);
// => false

_.isFloat(1.0);
// => false

_.isFloat("2.15");
// => true

isIncreasing

Signature: _.isIncreasing(value:Any...)

Checks whether the arguments are monotonically increasing values (i.e. each argument is greater than the previous argument.)

_.isIncreasing(1, 12, 15);
// => true

_.isIncreasing(1);
// => true

_.isIncreasing(5, 4);
// => false

isIndexed

Signature: _.isIndexed(value:Any)

Checks whether the value is “indexed.” An indexed value is one which accepts a numerical index to access its elements. (e.g. arrays and strings)

NOTE: lodash does not support cross-browser consistent use of strings as array-like values, so be wary in IE 8 when using string objects and in IE7 and earlier when using string literals & objects.

_.isIndexed("Socrates");
// => true

_.isIndexed({poison: "hemlock"});
// => false

isInstanceOf

Signature: _.isInstanceOf(value:Any, constructor:Function)

Checks whether the value is an instance of the constructor.

_.isInstanceOf(new Date(), Date);
// => true

_.isInstanceOf("Hippocrates", RegExp);
// => false

isInteger

Signature: _.isInteger(value:Any)

Checks whether the value is a numeric integer. A numeric value can be a string containing a number, a Number object, etc.

_.isInteger(18);
// => true

_.isInteger("18");
// => true

_.isInteger(2.5);
// => false

_.isInteger(-1);
// => true

isJSON

Signature: _.isJSON(value:Any)

Checks whether the value is valid JSON. See the spec for more information on what constitutes valid JSON.

NOTE: This function relies on JSON.parse which is not available in IE7 and earlier.

_.isJSON('{ "name": "Crockford" }');
// => true

_.isJSON({ name: "Crocket" });
// => false

isNegative

Signature: _.isNegative(value:Any)

Checks whether the value is a negative number.

_.isNegative(-2);
// => true

_.isNegative(5);
// => false

isNumeric

Signature: _.isNumeric(value:Any)

A numeric is something that contains a numeric value, regardless of its type. It can be a string containing a numeric value, exponential notation, a Number object, etc.

_.isNumeric("14");
// => true

_.isNumeric("fourteen");
// => false

isOdd

Signature: _.isOdd(value:Any)

Checks whether the value is an odd number.

_.isOdd(3);
// => true

_.isOdd(2);
// => false

_.isOdd({});
// => false

isPlainObject

Signature: _.isPlainObject(value:Any);

Checks whether the value is a “plain” object created as an object literal ({}) or explicitly constructed with new Object(). Instances of other constructors are not plain objects.

_.isPlainObject({});
// => true

_.isPlainObject(new Date());
// => false

_.isPlainObject([]);
// => false

isPositive

Signature: _.isPositive(value:Any)

Checks whether the value is a positive number.

_.isPositive(21);
// => true

_.isPositive(-3);
// => false

isSequential

Signature: _.isSequential(value:Any)

Checks whether the value is a sequential composite type (i.e. arrays and arguments).

_.isSequential(["Herodotus", "Thucidydes");
// => true

_.isSequential(new Date);
// => false

isValidDate

Signature: _.isValidDate(value:Any)

Checks whether the value is a valid date. That is, the value is both an instance of Date and it represents an actual date.

Warning: This function does not verify whether the original input to Date is a real date. For instance, new Date("02/30/2014") is considered a valid date because Date coerces that into a representation of 03/02/2014. To validate strings representing a date, consider using a date/time library like [Moment.js.][momentjs]

_.isValidDate(new Date("January 1, 1900"));
// => true

_.isValidDate(new Date("The Last Great Time War"));
// => false

isZero

Signature: _.isZero(value:Any)

Checks whether the value is 0.

_.isZero(0);
// => true

_.isZero("Pythagoras");
// => false