Can you pass in the value undefined.undefined as an argument to a function in JavaScript?

Question

Can you pass in the value undefined.undefined as an argument to a function in JavaScript?

I am looking to determine if an object contains a specific field with a value, and return a default value if it doesn't.

function checkValue(object, defaultValue) {
  if (!object) {
    console.log(defaultValue);
  } else {
    console.log(object);
  }
}

let testObject;
checkValue(testObject, 'this is the default value')

However, I want this function to handle checking values without requiring them to be passed explicitly...

If I try to pass:

testObject.field1.value

This will result in an error:

TypeError: Cannot read property 'field1' of undefined

Therefore, I need a way to pass any object and evaluate its value without using ternary ?: operators.

javascript

Answer 1

Answer №1

To effortlessly achieve this, utilize the power of Optional Chaining

function fetchData(data, defaultData) {
  if (!data) {
    console.log(defaultData)
  } else {
    console.log(data)
  }
}

let dataExample
fetchData(dataExample, dataExample?.field1?.value || 'Default value')

Answer 2

To effortlessly achieve this, utilize the power of Optional Chaining

function fetchData(data, defaultData) {
  if (!data) {
    console.log(defaultData)
  } else {
    console.log(data)
  }
}

let dataExample
fetchData(dataExample, dataExample?.field1?.value || 'Default value')

Answer 3

Answer №2

It is impossible to rectify the error within the function as it occurs prior to the function being invoked.

If you are utilizing a JS engine that has support for optional chaining, you can use

testFun(testVar?.foo.value, 'this is default value')

. If this feature is unavailable, it's necessary to reconsider your approach.

function testFun(value, defaultvalue) {
  if (!value) {
    console.log(defaultvalue)
  } else {
    console.log(value)
  }
}

let testVar
testFun(testVar?.foo.value, 'this is default value')

If not, a truthy check must be performed in some way.

function testFun(value, defaultvalue) {
  if (!value) {
    console.log(defaultvalue)
  } else {
    console.log(value)
  }
}

let testVar
testFun(testVar && testVar.foo && testVar.foo.value, 'this is default value')

Alternatively, you may need to modify the code to specify the field to be accessed and implement the checking logic within that function.

function testFun(obj, key, defaultvalue) {
  const value = obj && obj.key && obj.key.value;
  if (!value) {
    console.log(defaultvalue)
  } else {
    console.log(value)
  }
}

let testVar
testFun(testVar, 'foo', 'this is default value')

Answer 4

It is impossible to rectify the error within the function as it occurs prior to the function being invoked.

If you are utilizing a JS engine that has support for optional chaining, you can use

testFun(testVar?.foo.value, 'this is default value')

. If this feature is unavailable, it's necessary to reconsider your approach.

function testFun(value, defaultvalue) {
  if (!value) {
    console.log(defaultvalue)
  } else {
    console.log(value)
  }
}

let testVar
testFun(testVar?.foo.value, 'this is default value')

If not, a truthy check must be performed in some way.

function testFun(value, defaultvalue) {
  if (!value) {
    console.log(defaultvalue)
  } else {
    console.log(value)
  }
}

let testVar
testFun(testVar && testVar.foo && testVar.foo.value, 'this is default value')

Alternatively, you may need to modify the code to specify the field to be accessed and implement the checking logic within that function.

function testFun(obj, key, defaultvalue) {
  const value = obj && obj.key && obj.key.value;
  if (!value) {
    console.log(defaultvalue)
  } else {
    console.log(value)
  }
}

let testVar
testFun(testVar, 'foo', 'this is default value')

Answer 5

Answer №3

To handle this scenario, you have the option to utilize optional chaining.

const data = {
  field1: null
};

const value = data.field1?.value;

console.log('Value:', value);

If you opt not to use optional chaining, another approach is to destructure the object by ensuring that the parent of the nested value defaults to an empty object.

const data = {
  field1: {} // Must be initialized as an object for value extraction.
};

const { field1: { value } } = data;
 
console.log('Value:', value);

You could also consider using spread syntax to assign default values to the property, but remember to spread values at each level within the object.

const defaultProps = {
  field1: {
    value: null
  }
}

const data = {
  field1: {
    value: 'foo'
  }
};

const { field1 } = data;
const combined = { ...defaultProps, field1: field1 };

const { field1: { value } } = combined;
 
console.log('Value:', value);

Answer 6

To handle this scenario, you have the option to utilize optional chaining.

const data = {
  field1: null
};

const value = data.field1?.value;

console.log('Value:', value);

If you opt not to use optional chaining, another approach is to destructure the object by ensuring that the parent of the nested value defaults to an empty object.

const data = {
  field1: {} // Must be initialized as an object for value extraction.
};

const { field1: { value } } = data;
 
console.log('Value:', value);

You could also consider using spread syntax to assign default values to the property, but remember to spread values at each level within the object.

const defaultProps = {
  field1: {
    value: null
  }
}

const data = {
  field1: {
    value: 'foo'
  }
};

const { field1 } = data;
const combined = { ...defaultProps, field1: field1 };

const { field1: { value } } = combined;
 
console.log('Value:', value);

Answer 7

Answer №4

This solution has been successful for me:

function customFunction(fn, defaultVal) {
  try {
    if (fn() === undefined) {
      return defaultVal;
    } else {
      return fn();
    }
  } catch (error) {
    return defaultVal;
  }
}

let testData;
customFunction(() => testData.field1.value, 'this is the default value');

Answer 8

This solution has been successful for me:

function customFunction(fn, defaultVal) {
  try {
    if (fn() === undefined) {
      return defaultVal;
    } else {
      return fn();
    }
  } catch (error) {
    return defaultVal;
  }
}

let testData;
customFunction(() => testData.field1.value, 'this is the default value');

Can you pass in the value undefined.undefined as an argument to a function in JavaScript?

Answer №1

Answer №2

Answer №3

Answer №4

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