Example 1: Using instanceof Operator
// program to check if a variable is of function type
function testVariable(variable) {
if(variable instanceof Function) {
console.log('The variable is of function type');
}
else {
console.log('The variable is not of function type');
}
}
const count = true;
const x = function() {
console.log('hello')
};
testVariable(count);
testVariable(x);
Output
The variable is not of function type The variable is of function type
In the above program, the instanceof operator is used to check the type of variable.
Example 2: Using typeof Operator
// program to check if a variable is of function type
function testVariable(variable) {
if(typeof variable === 'function') {
console.log('The variable is of function type');
}
else {
console.log('The variable is not of function type');
}
}
const count = true;
const x = function() {
console.log('hello')
};
testVariable(count);
testVariable(x);
Output
The variable is not of function type The variable is of function type
In the above program, the typeof operator is used with strict equal to === operator to check the type of variable.
The typeof operator gives the variable data type. === checks if the variable is equal in terms of value as well as the data type.
Example 3: Using Object.prototype.toString.call() Method
// program to check if a variable is of function type
function testVariable(variable) {
if(Object.prototype.toString.call(variable) == '[object Function]') {
console.log('The variable is of function type');
}
else {
console.log('The variable is not of function type');
}
}
const count = true;
const x = function() {
console.log('hello')
};
testVariable(count);
testVariable(x);
Output
The variable is not of function type The variable is of function type
The Object.prototype.toString.call() method returns a string that specifies the object type.