Summary of JavaScript common scripts (3)

Extending string concatenation through arrays can lead to performance problems

function StringBuffer() {

    this.__strings__ = new Array();

}

StringBuffer.prototype.append = function (str) {

    this.__strings__.push(str);

    return this;

}

StringBuffer.prototype.toString = function () {

    return this.__strings__.join("");

}

var buffer = new StringBuffer();

buffer.append("Hello ").append("javascript");

var result = buffer.toString();

alert(result);    //Hello javascript

Source code: https: / / gist github. com/hehongwei44 / fe71f10e4d2d9295aeab

Page viewport scrollbar position of the auxiliary function

/* Determines the height and width of the current page */

function pageHeight() {

    return document.body.scrollHeight;

}

function pageWidth() {

    return document.body.scrollWidth;

}

/* Determine the horizontal and vertical positions of the scroll bar */

function scrollX() {

    var de = document.documentElement;

    return self.pageXOffset || (de && de.scrollLeft) || document.body.scrollLeft;

}

function scrollY() {

    var de = document.documentElement;

    return self.pageYOffset || (de && de.scrollTop) || document.body.scrollTop;

}

/* Determines the height and width of the browser viewport */

function windowHeight() {

    var de = document.documentElement;

    return self.innerHeight || (de && de.clientHeight) || document.body.clientHeight;

}

function windowWidth() {

    var de = document.documentElement;

    return self.innerWidth || (de && de.clientWidth) || document.body.clientWidth;

}

Source code: https: / / gist github. b9b7061d4defadb com hehongwei44/62907

A function that adjusts the transparency of an element

/* A function that adjusts the transparency of an element */

function setOpacity(elem, level) {

    //IE Processing transparency 

    if (elem.filters) {

        elem.style.filters = 'alpha(opacity=' + level + ')';

    } else {

        elem.style.opacity = level / 100;

    }

}

Source code: https: / / gist github. cd3b8439aff6a3c com hehongwei44/87839

Gets several generic functions for mouse position

/* Two general functions , Used to get the current position of the mouse relative to the entire page */

function getX(e) {

    e = e || window.event;

    return e.pageX || e.clientX + document.body.scrollLeft;

}

function getY(e) {

    e = e || window.event;

    return e.pageY || e.clientY + document.body.scrollTop;

}

/* Two functions that get the position of the mouse relative to the current element */

function getElementX(e) {

    return (e && e.layerX) || window.event.offsetX;

}

function getElementY(e) {

    return (e && e.layerY) || window.event.offsetY;

}

Source code: https: / / gist github. bd42baa491ef8 com hehongwei44/2732365

Use the cssdisplay attribute to switch 1 set of functions for element visibility

/**

 *  use display To hide the functions of the elements 

 * */

function hide(elem) {

    var curDisplay = getStyle(elem, 'display');
    if (curDisplay != 'none') {

        elem.$oldDisplay = curDisplay;

    }

    elem.style.display = 'none';

}

/**

 *  use display To display the functions of the elements 

 * */

function show(elem) {

    elem.style.display = elem.$oldDisplay || '';

}

Source code: https: / / gist github. com/hehongwei44 / b4192af8227d756bfda6

Style-related generic functions

/**

 *  Gets the specified element (elem) Style properties (name)

 * */

function getStyle(elem, name) {

    // If there is style[] In the , So it's already set ( And it's current )

    if (elem.style[name]) {

        return elem.style[name];

    }

    // Otherwise, , test IE The method of 

    else if (elem.currentStyle) {

        return elem.currentStyle[name];

    }

    // or W3C The method of 

    else if(document.defaultView && document.defaultView.getComputedStyle){

        name = name.replace(/(A-Z)/g, "-$1");

        name = name.toLowerCase();

        var s = document.defaultView.getComputedStyle(elem, "");

        return s && s.getPropertyValue(name);

    }

    // Otherwise, , The user is using a different browser 

    else {

        return null;

    }

}

Source code: https: / / gist github. Nine abf63536accd0f2eeb7 com hehongwei44 /

Gets the current height and width of the element

/**

 *  Gets the true height of the element 

 *  Rely on the getStyle See the function above. 

 * */

function getHeight(elem) {

    return parseInt(getStyle(elem, 'height'));

}

/**

 *  Gets the true width of the element 

 *  Rely on the getStyle See the function above 

 * */

function getWidth(elem) {

    return parseInt(getStyle(elem, 'width'));

}

Source code: https: / / gist github. com/hehongwei44 / b524ff25991d99625eb2

These are the common javascript scripts Shared in this article. I hope you enjoy them.