Display array elements with delay

问题

I have an arrays=[John; Alex; Mark], I wanna to show the elements of this array one by one by 3 second delay.

for (var i=0; i<=3; i++)
  {
     setTimeout(function(){x.innerHTML=s[i]},3000)
  }

It seems very simple problem, but I can't figure out.

回答1:

your loop runs four times, not three
setTimeout starts with a lower case s
your delay should be 3000 for 3 seconds, not 2000
your delay should be 3000 * i, not 3000 or they'll all fire at once
you can't use loop variables inside an asynchronous callback without special precautions - the callbacks will all see the last value assigned to i, not the values it had as you went through the loop.

This works, and completely avoids the loop variable issue:

var s = ['John', 'Mark', 'Alex'];
var i = 0;

(function loop() {
    x.innerHTML = s[i];
    if (++i < s.length) {
        setTimeout(loop, 3000);  // call myself in 3 seconds time if required
    }
})();      // above function expression is called immediately to start it off

Note how it uses "pseudo-recursion" to trigger the next iteration 3000ms after the completion of the previous iteration. This is preferable to having n outstanding timers all waiting at the same time.

See http://jsfiddle.net/alnitak/mHQVz/

回答2:

http://jsfiddle.net/rlemon/mHQVz/1/

I got to tinkering... albeit this is probably not the best solution it was fun.

var x = document.getElementById('x'),
    s = ['John', 'Mark', 'Alex'];

(function loop() {
    s.length && (x.innerHTML = s.shift(), setTimeout(loop, 3000));
})();

Alnitak's solution is alot better. However they both would work (his is just more readable and less hacky also does not destroy the array).

回答3:

Try

var s=['John', 'Alex', 'Mark'];
var x = document.getElementById('x');

function display(i){
    if(i >= s.length){
        i = 0;
    }

    x.innerHTML = s[i];
    setTimeout(function(){
       display(i + 1)
    }, 2000)
}

display(0)

Demo: Fiddle

回答4:

If you do not use closure, you will end up with i being undefined. This is because in each iteration you are overriding what i is. By the time it finishes, it will be undefined. Using a closure will preserve i.

On another note, it's kind of pointless to hard code in values (i.e. i<3) when you can just check for length. This way, if s ever changes, you for loop will still grab everything.

var s = ['john','mark','brian'];
for (var i = 0; i < s.length; i++) {
    (function(i) {
        setTimeout(function() {
            x.innerHTML = s[i];
        }, 3000*(i+1));
    })(i);
}

回答5:

Your code won't work, since you set four timeouts of 2000 milliseconds (i.e. 2 seconds) at a time. You'd better use closure that sets three timeouts (by number of elements in array) with 3000 milliseconds of delay. It can be done with the following code (note that setTimeout is written from the small letter):

var s = ["John", "Alex", "Mark"];
for (var i = 0; i < s.length; i++) {
    (function(i) {
        setTimeout(function() {
            x.innerHTML = s[i];
        }, 3000 * i);
    })(i);
}

DEMO: http://jsfiddle.net/6Ne6z/

回答6:

You can use setInterval to show elements one by one after 3 seconds delay:

s=["John", "Alex", "Mark"];

var i = 0;
var id = setInterval(function(){                
            if(i > s.length) {                  
                clearInterval(id);                  
            }
            else{
                console.log(s[i++]);
            }
}, 3000);

回答7:

Try this without pseudo-recursion

var arr = [10,20,30,40]; // your array
var i = 0;
var interval = 2000 // 2 sec, you can add your time required
function callInterval() {
// set a variable for setInterval
	var time = setInterval(()=>{
		console.log('['+arr[i]+','+i+']');
		i++; 
		if(i==arr.length){
			this.clearInterval(time);// clear the interval after the index
		}
		}, interval);
}

callInterval();

回答8:

this will also help:

const fruits = ['apple', 'banana', 'mango', 'guava'];
let index = 0;
const primtMe = (value, i) => {
    if (i < fruits.length) {
        setTimeout(() => {
            console.log(i + ' value = ' + value)
            primtMe(fruits[i + 1], i + 1)
        }, 3000);
    } else {
        return;
    }
}

primtMe(fruits[index], index)

来源：https://stackoverflow.com/questions/15788472/display-array-elements-with-delay

标签

javascript

settimeout