I understand there is no block level scope for var i ; however, in the following code, d.push(); is executed after the initialisation of i, why i here remains undefined?
var d = [];
for (var i = 0; i < 3; i++) {
d.push(function(i) {
console.log('iterator: ' + i);
});
}
d[0]();//undefined
Any thoughts will be appreciated
You can push an argument-bound version of the anonymous function by using .bind() thereby ensuring the value of the first argument.
var d = [];
for (var i = 0; i < 3; i++) {
d.push((function(i) {
console.log('iterator: ' + i);
}).bind(this, i));
}
d[0](); // iterator: 0
d[1](); // iterator: 1
d[2](); // iterator: 2
Here's my solution:
var d = [];
function newFunction(i) {
var k = i;
return function() {
console.log('iterator: ' + k);
}
}
for (var i = 0; i < 3; i++) {
d.push(
newFunction(i)
);
}
d[0]();
d[1]();
This works because when you create the new function, it creates a variable scope that doesn't change with your for loop. It saves the state of i on each iteration so that when you call them again, it runs with the i it was originally declared with.
function(i) { console.log('iterator: ' + i); }which has a parameteri. But when you call the function,d[0]();, you didn't pass any argument.