What is the basic structure of javascript

The basic structure of JavaScript is: 1. ECMAScript, all objects in js are derived from a large object in ECMAScript; 2. DOM, the document object model, is the HTML tree; 3. BOM, the browser object Model, the browser manufacturer will encapsulate the basic information of the browser in the BOM object.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

1. The javascript scripting language is composed of three parts. That is, the core: ECMAScript, dom, bom.

a).ECMAScript uses the browser as the host, you can read it It is a base function. All objects in JavaScript are derived from a large object in ECMAScript. Since different browsers have different implementations of ECMAScript (based on w3c), the js code in different browsers on the market It needs to be compatible.

b). DOM is the document object model, which is the HTML tree. DOM allows you to use js to obtain the objects of nodes in the DOM tree so that you can operate on HTML elements.

c). BOM is the browser object model. Browser manufacturers will encapsulate the basic information of the browser in the BOM object. Such as the various widths and heights of the window. Browser version, core and other information.

2. I personally think that JavaScript is mainly used for static HTML and user interaction. As the saying goes: make html elements move. For example: add and delete dom tree nodes. Make pixel animations, add event listeners to html controls, etc. I have to say that there is also ajax, which is an asynchronous request triggered by js.

3. The most commonly used methods of the window object are probably location (used to jump to pages and redirect), escape (series) used to encode URLs. navigator (used to obtain basic browser information), setTimeout timer, offsetWidth\offsetHeight\clientWidth, etc. (get window height\width). For more methods, you can go to w3cschool to see.

4. The Date object method is as follows

getDate() Returns a from the Date object A day in the month (1 ~ 31).

getDay() returns the day of the week (0 ~ 6) from the Date object.

getMonth() returns the month (0 ~ 11) from the Date object.

getFullYear() Returns the year as a four-digit number from a Date object.

getYear() Please use getFullYear() method instead.

getHours() returns the hours (0 ~ 23) of the Date object.

getMinutes() returns the minutes (0 ~ 59) of the Date object.

getSeconds() returns the seconds of the Date object (0 ~ 59).

getMilliseconds() returns the milliseconds (0 ~ 999) of the Date object.

getTime() Returns the number of milliseconds since January 1, 1970.

getTimezoneOffset() Returns the difference in minutes between local time and Greenwich Mean Time (GMT).

getUTCDate() Returns the day of the month (1 ~ 31) from a Date object based on universal time.

getUTCDay() Returns the day of the week (0 ~ 6) from a Date object based on universal time.

getUTCMonth() Returns the month (0 ~ 11) from the Date object according to universal time.

getUTCFullYear() Returns the four-digit year from a Date object based on universal time.

getUTCHours() Returns the hour (0 ~ 23) of the Date object according to universal time.

getUTCMinutes() Returns the minutes (0 ~ 59) of the Date object according to universal time.

getUTCSeconds() Returns the seconds (0 ~ 59) of the Date object according to universal time.

getUTCMilliseconds() returns the milliseconds (0 ~ 999) of the Date object according to universal time.

parse() Returns the number of milliseconds from midnight on January 1, 1970 to the specified date (string).

setDate() sets the day of the month (1 ~ 31) in the Date object.

setMonth() sets the month (0 ~ 11) in the Date object.

setFullYear() Sets the year (four digits) in the Date object.

setYear() Please use the setFullYear() method instead.

setHours() Sets the hours (0 ~ 23) in the Date object.

setMinutes() Sets the minutes (0 ~ 59) in the Date object.

setSeconds() Sets the seconds (0 ~ 59) in the Date object.

setMilliseconds() Sets the milliseconds (0 ~ 999) in the Date object.

setTime() Sets a Date object in milliseconds.

setUTCDate() Sets the day of the month (1 ~ 31) in the Date object according to universal time.

setUTCMonth() Sets the month (0 ~ 11) in the Date object according to universal time.

setUTCFullYear() Sets the year (four digits) in the Date object according to universal time.

setUTCHours() Sets the hour (0 ~ 23) in the Date object according to universal time.

setUTCMinutes() Sets the minutes (0 ~ 59) in the Date object according to universal time.

setUTCSeconds() Sets the seconds (0 ~ 59) in the Date object according to universal time.

setUTCMilliseconds() Sets the milliseconds (0 ~ 999) in the Date object according to universal time.

toSource() Returns the source code of the object.

toString() Converts a Date object to a string.

toTimeString() Converts the time part of the Date object to a string.

toDateString() Converts the date part of the Date object to a string.

toGMTString() Please use toUTCString() method instead.

toUTCString() Converts a Date object to a string according to universal time.

toLocaleString() Converts the Date object to a string according to the local time format.

toLocaleTimeString() Converts the time part of the Date object into a string according to the local time format.

toLocaleDateString() Converts the date part of the Date object into a string according to the local time format.

UTC() Returns the number of milliseconds from January 1, 1970 to the specified date according to universal time.

valueOf() returns the original value of the Date object.

5. The difference between the setTimeout() method and the setInterval() method

setTimeout: Wait for the specified milliseconds before executing the callback function. This method is only executed once. That is, it is executed once after delaying the specified time. .

Of course, you can also make a loop callback. That is, set setTimeout in the callback function. When making animations that take up a lot of memory, setTimeout loop callbacks are generally used instead of setInterval. Because setTimeout is The next setTimeout is initiated only when the callback is executed. And setInterval is executed every specified time. It does not care whether the code in your callback has been executed. This will cause problems. If the code executed in your callback function is more time-consuming Time. setTimeout will wait for your callback function to execute the specified code segment before initiating the next setTimeout. This ensures that your animation can be executed normally even if it is stuck. You can imagine the execution effect of setInterval. It will make Your animation becomes messy.

setInterval: Execute the callback function every specified time. This method is suitable for repeatedly executing the callback function that takes up less resources. For example, you display a dynamic clock on the page. There is no need to make a setTimeout loop call.

[Recommended learning: javascript advanced tutorial]

The above is the detailed content of What is the basic structure of javascript. For more information, please follow other related articles on the PHP Chinese website!