阻止页面中的 JavaScript 函数
2021-12-01
145
我网站的 JS 文件中有一个用于滑块的 javascript 函数。当我们处于未调用滑块或没有触发元素的页面时，它会在控制台中显示错误“Uncaught TypeError：无法读取 null 的属性（读取‘querySelector’）”，滑块在页面中时不会显示此错误。
我想知道如何避免此错误，以及如何防止此函数在没有此滑块的页面中加载？
function slider(set) {
const sliderContainer = document.querySelector(set.name),
slider = sliderContainer.querySelector('.slider'),
sliderItem = slider.querySelectorAll('.slider__item'),
sliderArrows = sliderContainer.querySelectorAll('.arrows__item');
let dotsCreate,
dotsClass,
dotsFunk,
numberSlider,
numberSliderWork,
sliderExecutionLine,
sliderExecutionLineWork;
// calculate the maximum width of all slides
function forSliderItem(t) {
t = 0;
for(let i = 0; i < sliderItem.length - 1; i++) {
t += sliderItem[i].clientWidth;
}
return t;
}
let maxWidth = forSliderItem(sliderItem), // maximum width of all slides
slidWidth = 0, // main variable for calculating the movement of the slider
count = 0; // counter
//===== flip left
sliderArrows[0].addEventListener('click', function() {
if(count !== 0) {
count--;
slidWidth -= sliderItem[count].clientWidth;
slider.style.transform = `translateX(-${slidWidth}px)`;
} else {
count = sliderItem.length - 1;
slidWidth = maxWidth;
slider.style.transform = `translateX(-${slidWidth}px)`;
}
if(set.dots) {
dotsFunk();
}
if(set.numberSlid) {
numberSliderWork(count);
}
if(set.line) {
sliderExecutionLineWork(count);
}
});
//===== flip right
sliderArrows[1].addEventListener('click', function() {
if(count < sliderItem.length - 1) {
count++;
slidWidth += sliderItem[count].clientWidth;
slider.style.transform = `translateX(-${slidWidth}px)`;
} else {
count = 0;
slidWidth = 0;
slider.style.transform = `translateX(-${slidWidth}px)`;
}
if(set.dots) {
dotsFunk();
}
if(set.numberSlid) {
numberSliderWork(count);
}
if(set.line) {
sliderExecutionLineWork(count);
}
});
//===== dots
if(set.dots) {
dotsCreate = function() {
const dotContainer = document.createElement('div'); // create dots container
dotContainer.classList.add('dots');
// create the required number of dots and insert a container into the dots
sliderItem.forEach(() => {
let dotsItem = document.createElement('span');
dotContainer.append(dotsItem);
});
sliderContainer.append(dotContainer);
};
dotsCreate();
// add the class to the desired dots, and remove from the rest
dotsClass = function(remove, add) {
remove.classList.remove('dots_active');
add.classList.add('dots_active');
};
// move slides by clicking on the dot
dotsFunk = function() {
const dotsWork = sliderContainer.querySelectorAll('.dots span'); // we get dots
dotsWork.forEach((item, i) => {
dotsClass(dotsWork[i], dotsWork[count]);
item.addEventListener('click', function() {
count = i;
// multiply the slide size by the number of the dots, and get the number by which you need to move the slider
slidWidth = sliderItem[0].clientWidth * i;
slider.style.transform = `translateX(-${slidWidth}px)`;
for(let j = 0; j < dotsWork.length; j++) {
dotsClass(dotsWork[j], dotsWork[count]);
}
if(set.dots && set.numberSlid) {
numberSliderWork(count);
}
if(set.line) {
sliderExecutionLineWork(count);
}
});
});
};
dotsFunk();
}
//===== count slider
if(set.numberSlid) {
numberSlider = function(item) {
const countContainer = document.createElement('div'),
sliderNumber = document.createElement('span'),
slash = document.createElement('span'),
allSliderNumber = document.createElement('span');
casClient = document.createElement('p');
sliderNumber.innerHTML = item + 1;
casClient.innerHTML = 'Cas client N°';
slash.innerHTML = '/';
allSliderNumber.innerHTML = sliderItem.length;
countContainer.classList.add('count-slides');
countContainer.append(casClient, sliderNumber, slash, allSliderNumber);
sliderContainer.append(countContainer);
};
numberSlider(0);
numberSliderWork = function(item) {
const sliderNumberNow = sliderContainer.querySelector('.count-slides span');
sliderNumberNow.innerHTML = item + 1;
if(set.line) {
sliderExecutionLineWork(item);
}
};
}
}
slider({
name: ".video_users",
numberSlid: true
});
<!DOCTYPE html>
<html lang="fr">
<head>
<title>Example of a page without the slider</title>
</head>
<body class="error_404">
<h1>Example of a page without the slider</h1>
<script src="media/js/faveod.js" async></script>
</body>
</html>
2个回答
如果不希望显示错误，则只需在元素不存在时返回即可。
const sliderContainer = document.querySelector(set.name);
if (!sliderContainer) return;
const slider = sliderContainer.querySelector('.slider'),
sliderItem = slider.querySelectorAll('.slider__item'),
sliderArrows = sliderContainer.querySelectorAll('.arrows__item');
如果您希望它仅在某些页面上执行，则只需添加：
if (location.pathname !== '/the/page/with/slider') return;
到函数的开头
skara9
2021-12-01
/*
* SCROLLBAR 2 COLUMN / SOLUTIONS
*/
var ssb = {
aConts : [],
mouseY : 0,
N : 0,
asd : 0, /*active scrollbar element*/
sc : 0,
sp : 0,
to : 0,
// constructor
scrollbar : function (cont_id) {
var cont = document.getElementById(cont_id);
// perform initialization
if (! ssb.init()) return false;
var cont_clone = cont.cloneNode(false);
cont_clone.style.overflow = "hidden";
cont.parentNode.appendChild(cont_clone);
cont_clone.appendChild(cont);
cont.style.position = 'absolute';
cont.style.left = cont.style.top = '0px';
cont.style.width = cont.style.height = '100%';
// adding new container into array
ssb.aConts[ssb.N++] = cont;
cont.sg = false;
//creating scrollbar child elements
cont.st = this.create_div('ssb_st', cont, cont_clone);
cont.sb = this.create_div('ssb_sb', cont, cont_clone);
cont.su = this.create_div('ssb_up', cont, cont_clone);
cont.sd = this.create_div('ssb_down', cont, cont_clone);
// on mouse down processing
cont.sb.onmousedown = function (e) {
if (! this.cont.sg) {
if (! e) e = window.event;
ssb.asd = this.cont;
this.cont.yZ = e.screenY;
this.cont.sZ = cont.scrollTop;
this.cont.sg = true;
// new class name
this.className = 'ssb_sb ssb_sb_down';
}
return false;
}
// on mouse down on free track area - move our scroll element too
cont.st.onmousedown = function (e) {
if (! e) e = window.event;
ssb.asd = this.cont;
ssb.mouseY = e.clientY + document.body.scrollTop + document.documentElement.scrollTop;
for (var o = this.cont, y = 0; o != null; o = o.offsetParent) y += o.offsetTop;
this.cont.scrollTop = (ssb.mouseY - y - (this.cont.ratio * this.cont.offsetHeight / 2) - this.cont.sw) / this.cont.ratio;
this.cont.sb.onmousedown(e);
}
// onmousedown events
cont.su.onmousedown = cont.su.ondblclick = function (e) { ssb.mousedown(this, -1); return false; }
cont.sd.onmousedown = cont.sd.ondblclick = function (e) { ssb.mousedown(this, 1); return false; }
//onmouseout events
cont.su.onmouseout = cont.su.onmouseup = ssb.clear;
cont.sd.onmouseout = cont.sd.onmouseup = ssb.clear;
// on mouse over - apply custom class name: ssb_sb_over
cont.sb.onmouseover = function (e) {
if (! this.cont.sg) this.className = 'ssb_sb ssb_sb_over';
return false;
}
// on mouse out - revert back our usual class name 'ssb_sb'
cont.sb.onmouseout = function (e) {
if (! this.cont.sg) this.className = 'ssb_sb';
return false;
}
// onscroll - change positions of scroll element
cont.ssb_onscroll = function () {
this.ratio = (this.offsetHeight - 2 * this.sw) / this.scrollHeight;
this.sb.style.top = Math.floor(this.sw + this.scrollTop * this.ratio) + 'px';
}
// scrollbar width
cont.sw = 16;
// start scrolling
cont.ssb_onscroll();
ssb.refresh();
// binding own onscroll event
cont.onscroll = cont.ssb_onscroll;
return cont;
},
// initialization
init : function () {
if (window.oper || (! window.addEventListener && ! window.attachEvent)) { return false; }
// temp inner function for event registration
function addEvent (o, e, f) {
if (window.addEventListener) { o.addEventListener(e, f, false); ssb.w3c = true; return true; }
if (window.attachEvent) return o.attachEvent('on' + e, f);
return false;
}
// binding events
addEvent(window.document, 'mousemove', ssb.onmousemove);
addEvent(window.document, 'mouseup', ssb.onmouseup);
addEvent(window, 'resize', ssb.refresh);
return true;
},
// create and append div finc
create_div : function(c, cont, cont_clone) {
var o = document.createElement('div');
o.cont = cont;
o.className = c;
cont_clone.appendChild(o);
return o;
},
// do clear of controls
clear : function () {
clearTimeout(ssb.to);
ssb.sc = 0;
return false;
},
// refresh scrollbar
refresh : function () {
for (var i = 0, N = ssb.N; i < N; i++) {
var o = ssb.aConts[i];
o.ssb_onscroll();
o.sb.style.width = o.st.style.width = o.su.style.width = o.su.style.height = o.sd.style.width = o.sd.style.height = o.sw + 'px';
o.sb.style.height = Math.ceil(Math.max(o.sw * .5, o.ratio * o.offsetHeight) + 1) + 'px';
}
},
// arrow scrolling
arrow_scroll : function () {
if (ssb.sc != 0) {
ssb.asd.scrollTop += 6 * ssb.sc / ssb.asd.ratio;
ssb.to = setTimeout(ssb.arrow_scroll, ssb.sp);
ssb.sp = 32;
}
},
/* event binded functions : */
// scroll on mouse down
mousedown : function (o, s) {
if (ssb.sc == 0) {
// new class name
o.cont.sb.className = 'ssb_sb ssb_sb_down';
ssb.asd = o.cont;
ssb.sc = s;
ssb.sp = 100;
ssb.arrow_scroll();
}
},
// on mouseMove binded event
onmousemove : function(e) {
if (! e) e = window.event;
// get vertical mouse position
ssb.mouseY = e.screenY;
if (ssb.asd.sg) ssb.asd.scrollTop = ssb.asd.sZ + (ssb.mouseY - ssb.asd.yZ) / ssb.asd.ratio;
},
// on mouseUp binded event
onmouseup : function (e) {
if (! e) e = window.event;
var tg = (e.target) ? e.target : e.srcElement;
if (ssb.asd && document.releaseCapture) ssb.asd.releaseCapture();
// new class name
if (ssb.asd) ssb.asd.sb.className = (tg.className.indexOf('scrollbar') > 0) ? 'ssb_sb ssb_sb_over' : 'ssb_sb';
document.onselectstart = '';
ssb.clear();
ssb.asd.sg = false;
}
}
window.onload = function() {
ssb.scrollbar('container'); // scrollbar initialization
}
Tony
2021-12-01