for in loops javascript

for (var i; i < 10; i++) {
  
}let array = ['Item 1', 'Item 2', 'Item 3'];

array.forEach(item => {
	console.log(item); // Logs each 'Item #'
});Example:
const object = { a: 1, b: 2, c: 3 };

for (const property in object) {
  console.log(`${property}: ${object[property]}`);
}

// expected output:
// "a: 1"
// "b: 2"
// "c: 3"


Syntax:
for (variable in object)
  statementconst array1 = ['a', 'b', 'c'];

array1.forEach(element => console.log(element));function diagonalDifference(arr) {
    // Write your code here
    // return (arr); 11,2,4,4,5,6,10,8,-12
    let n = arr.length;
    let pri,sec = 0;

    pri = sec = 0; //initialize both diagonal sum to 0
    for (let i= 0; i < n; i++) {
        //console.log( "PRI(arr)= ", i,i);
        //console.log( arr[i][i]);
        //console.log( "SEC(arr)= ", i,n-i-1);
        //console.log( arr[i][n-i-1]);
        pri += arr[i][i];
        sec += arr[i][n - i - 1]; 
    }
	
  	// return |x| is the absolute value of x
    if(pri==sec){
        return (0);
    }else {
        if (pri>sec){
            return (pri-sec);
        }else{
            return (sec-pri);
        }
    }
}for(const key in object){
  	// do stuff
}
// goes through the keys of an object