function pow(x,n) // <- no space between arguments
{ // <- figure bracket on a separate line
 let result=1; // <- no spaces before or after =
 for(let i=0;i<n;i++) {result*=x;} // <- no spaces
 // the contents of { ... } should be on a new line
 return result;
}
let x=prompt("x?",''), n=prompt("n?",'') // <-- technically possible,
// but better make it 2 lines, also there's no spaces and missing ;
if (n<=0) // <- no spaces inside (n <= 0), and should be extra line above it
{ // <- figure bracket on a separate line
 // below - long lines can be split into multiple lines for improved readability
 alert(`Power ${n} is not supported, please enter an integer number greater than zero`);
}
else // <- could write it on a single line like "} else {"
{
 alert(pow(x,n)) // no spaces and missing ;
}

function pow(x, n) {
 let result = 1;
 for (let i = 0; i < n; i++) {
 result *= x;
 }
 return result;
}
let x = prompt("x?", "");
let n = prompt("n?", "");
if (n <= 0) {
 alert(`Power ${n} is not supported,
 please enter an integer number greater than zero`);
} else {
 alert( pow(x, n) );
}