Javascript basics - Coercion

Coercion

Coercion in JavaScript refers to the process of converting a value from one type to another.

String Concatenation (Number to String)

var msg1 = "There are ";
var numStudents = 16;
var msg2 = " students.";
console.log(msg1 + numStudents + msg2);
// "There are 16 students."

When you use the + operator between a string and a number, JavaScript converts the number to a string before concatenating. So, numStudents gets implicitly converted to a string, and then all three strings are concatenated together.

var numStudents = 16;

console.log(`There are ${numStudents + ""} students.`);
// "There are 16 students."

The numStudents + "" part ensures that the numeric value of numStudents is coerced into a string before being included in the template literal.

String to Number

function addAStudent(numStudents) {
  return numStudents + 1;
}
addAStudent(Number(studentInputElem.value));
// 17

The Number function is used to convert the value obtained from studentInputElem.value into a number.

Boolean Coercion

In JavaScript, boolean coercion involves converting values to either true or false based on their truthiness or falsiness. The falsy values in JavaScript include false, 0, "" (empty string), null, undefined, and NaN. All other values are considered truthy.

while (newStudents.length > 0) {
  enrollStudent(newStudents.pop());
}

newStudents.length > 0 is checking whether the length of the newStudents array is greater than 0. If the length is greater than 0, it evaluates to true, indicating that there are still elements in the array. The while loop continues to execute as long as the condition in parentheses is true. The boolean coercion happens implicitly in the while loop condition, where the truthiness of the expression is determined by whether the array length is greater than 0.

Vivienne Reay