What is for each...in a statement in JavaScript?

The for each...in loop was a non-standard JavaScript feature that iterated over the values of object properties. However, it has been deprecated and removed from modern JavaScript engines.

Important: The for each...in statement is deprecated and no longer supported. Use modern alternatives like for...of, Object.values(), or forEach() instead.

Syntax (Deprecated)

The original syntax was:

for each (variablename in object) {
   statement or block to execute
}

Why It Was Deprecated

The for each...in statement was:

• Non-standard and only supported in Firefox
• Confusing because it mixed concepts from for...in and array iteration
• Replaced by better, standardized alternatives

Modern Alternatives

Using Object.values() with forEach()

var myObj = {myProp1: 30, myProp2: 40};
var sum = 0;

Object.values(myObj).forEach(function(value) {
    sum += value;
});

console.log(sum);

70

Using for...of with Object.values()

var myObj = {myProp1: 30, myProp2: 40};
var sum = 0;

for (var value of Object.values(myObj)) {
    sum += value;
}

console.log(sum);

70

Using for...in (for keys)

var myObj = {myProp1: 30, myProp2: 40};
var sum = 0;

for (var key in myObj) {
    sum += myObj[key];
}

console.log(sum);

70

Comparison of Modern Approaches

Conclusion

The for each...in statement is obsolete and should not be used. Modern JavaScript provides better alternatives like Object.values() with forEach() or for...of loops for iterating over object values.