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isDefined

function isDefined<T>(t?): T & 
  | null
  | {
};

Test that a value t is set to something and return it, throws on undefined.

This is handy when selecting using an index to eliminiate the infered undefined type.

Type Parameters​

Type Parameter
T

Parameters​

ParameterType
t?T

Returns​

T & | null | { }

Example​

console.log(isDefined('')); // =\> ''
console.log(isDefined(0)); // =\> 0
console.log(isDefined(false)); // =\> false
console.log(isDefined(null)); // =\> null
console.log(isDefined(undefined)); // will throw