This is an exract from casperjs JS :
function getPrices() {
var price = document.querySelectorAll('#InvoiceDetailGrid tbody');
return Array.prototype.map.call(price, function(elem) {
return elem.textContent;
});
}
Why use Array.prototype.map.call: wouldn't be possible to use simply:
price.map() ?
Because price is an array-like(NodeList) object, not an array.
With Array.prototype.map, you are taking a method of Array and use the array-like object as object for mapping.
price itself has no map method. That's why Array.prototype.map.call is needed
Why use Array.prototype.map.call: wouldn't be possible to use simply: price.map() ?
Because you want to call the function you pass in the call as a second argument with a specified this. The this in your case is the first argument: price, The price is an array like object (it has a length property), but it hasn't the methods that arrays have. So the only way you could call the map function on an array like object is this.
If price would have been an array, you could call the map as usually:
price.map(function(item){//...});
The fact that it's not an array routes you to this solution.
Because document.querySelectorAll returns an array-like object which does not have .map method. It doesn't return actual array.
pricehas no methodmap…