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'Proprieta' e metodi dell'array
'Il vero punto di forza degli array JavaScript sono le proprieta' e i metodi dell'array integrato: 'Esempi 'var x = cars.length; // The length property returns the number of elements 'var y = cars.sort(); // The sort() method sorts arrays 'I metodi delle matrici sono trattati nei prossimi capitoli. 'La lunghezza Proprieta' 'La lengthproprieta' di un array restituisce la lunghezza di un array (il numero di elementi dell'array). 'Esempio 'var fruits = ["Banana", "Orange", "Apple", "Mango"]; 'fruits.length; // the length of fruits is 4 https://www.w3schools.com/js/tryit.asp?filename=tryjs_array_length <!DOCTYPE html> <html> <body> <h2>JavaScript Arrays</h2> <p>The length property returns the length of an array.</p> <p id="demo"></p> <script> var fruits = ["Banana", "Orange", "Apple", "Mango"]; document.getElementById("demo").innerHTML = fruits.length; </script> </body> </html> 'La length proprieta' e' sempre uno piu' del piu' alto indice di array. 'Accesso al primo elemento dell'array 'Esempio 'fruits = ["Banana", "Orange", "Apple", "Mango"]; 'var first = fruits[0]; https://www.w3schools.com/js/tryit.asp?filename=tryjs_array_first <!DOCTYPE html> <html> <body> <h2>JavaScript Arrays</h2> <p>JavaScript array elements are accesses using numeric indexes (starting from 0).</p> <p id="demo"></p> <script> var fruits = ["Banana", "Orange", "Apple", "Mango"]; var first = fruits[0]; document.getElementById("demo").innerHTML = first; </script> </body> </html> 'Accesso all'elemento Ultima matrice 'Esempio 'fruits = ["Banana", "Orange", "Apple", "Mango"]; 'var last = fruits[fruits.length - 1]; https://www.w3schools.com/js/tryit.asp?filename=tryjs_array_last <!DOCTYPE html> <html> <body> <h2>JavaScript Arrays</h2> <p>JavaScript array elements are accesses using numeric indexes (starting from 0).</p> <p id="demo"></p> <script> var fruits = ["Banana", "Orange", "Apple", "Mango"]; var last = fruits[fruits.length-1]; document.getElementById("demo").innerHTML = last; </script> </body> </html> 'Elementi di Array Looping 'Il modo piu' sicuro per eseguire il ciclo di un array, utilizza un forciclo: 'Esempio 'var fruits, text, fLen, i; 'fruits = ["Banana", "Orange", "Apple", "Mango"]; 'fLen = fruits.length; 'text = "<ul>"; 'for (i = 0; i < fLen; i++) { ' text += "<li>" + fruits[i] + "</li>"; '} 'text += "</ul>"; https://www.w3schools.com/js/tryit.asp?filename=tryjs_array_loop <!DOCTYPE html> <html> <body> <h2>JavaScript Arrays</h2> <p>The best way to loop through an array is using a standard for loop:</p> <p id="demo"></p> <script> var fruits, text, fLen, i; fruits = ["Banana", "Orange", "Apple", "Mango"]; fLen = fruits.length; text = "<ul>"; for (i = 0; i < fLen; i++) { text += "<li>" + fruits[i] + "</li>"; } text += "</ul>"; document.getElementById("demo").innerHTML = text; </script> </body> </html> 'Puoi anche usare la Array.forEach()funzione: 'Esempio 'var fruits, text; 'fruits = ["Banana", "Orange", "Apple", "Mango"]; 'text = "<ul>"; 'fruits.forEach(myFunction); 'text += "</ul>"; 'function myFunction(value) { ' text += "<li>" + value + "</li>"; '} https://www.w3schools.com/js/tryit.asp?filename=tryjs_array_loop_foreach <!DOCTYPE html> <html> <body> <h2>JavaScript Arrays</h2> <p>Array.forEach() calls a function for each array element.</p> <p>Array.forEach() is not supported in Internet Explorer 8 or earlier.</p> <p id="demo"></p> <script> var fruits, text; fruits = ["Banana", "Orange", "Apple", "Mango"]; text = "<ul>"; fruits.forEach(myFunction); text += "</ul>"; document.getElementById("demo").innerHTML = text; function myFunction(value) { text += "<li>" + value + "</li>"; } </script> </body> </html> |