1. Timed output 0,1,2
Modify the following code so that the timer outputs 0,1,2 in sequence
for (var i = 0; i < 3; i++) {
console.log('gsy--0', new Date().getTime(),i)
setTimeout(() => {
console.log('gsy---1', new Date().getTime(),i)
}, 1000);
}
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for (let i = 0; i < 3; i++) {
console.log('gsy--0', new Date().getTime(),i)
setTimeout(() => {
console.log('gsy---1', new Date().getTime(),i)
}, 1000);
}
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for (let i = 0; i < 3; i++) {
console.log('gsy--0', new Date().getTime(),i)
setTimeout(() => {
console.log('gsy---1', new Date().getTime(),i)
}, i*1000);
}
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May refer to
Task queue – event pool
The new Queue (). The task (1000, () = > console. The log (1)). The task (2000, () = > console. The log (2)). The task (3000, () = > console. The log (3)). The start () to implement this function, After start(), wait 1 second to output 1, wait another 2 seconds to output 2, and wait another 3 seconds to output 3.Copy the code- The chain call to Promise’s then
- The chain call returns this
The Class writing
class Queue {
constructor() {
console.log('gsy---constructor', new Date().getTime())
this.queue = []
}
task(times, cb) {
this.queue.push({
times,
cb
})
console.log('gsy---task', this.queue)
return this
}
async start() {
let result = Promise.resolve()
while (this.queue.length > 0) {
const {
times,
cb
} = this.queue.shift()
result = result.then(() => {
console.log('gsy---then', new Date().getTime())
return new Promise((resolve) => {
setTimeout(() => {
cb();
console.log('gsy---resolve', new Date().getTime())
resolve()
}, times)
})
})
console.log('gsy---result', new Date().getTime())
}
}
}
new Queue()
.task(1000, () => {
console.log(1)
})
.task(2000, () => {
console.log(2)
})
.task(3000, () => {
console.log(3)
})
.start()
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ES5
function Quene() {
this.quene = [];
}
Quene.prototype.task = function (time, callback) {
this.quene.push({
time,
callback
});
return this;
};
Quene.prototype.start = function () {
const quene = this.quene;
let result = Promise.resolve();
quene.forEach((item) => {
result = result.then(() => {
console.log('gsy---then', new Date().getTime())
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve(item.callback());
console.log('gsy---resolve', new Date().getTime())
}, item.time);
});
});
console.log('gsy---result', result)
});
return result;
};
new Quene()
.task(1000, () => {
console.log(1)
})
.task(2000, () => {
console.log(2)
})
.task(3000, () => {
console.log(3)
})
.start()
Copy the code- Async await time stacking (not recommended)
async function one() {
console.log('gsy---0', new Date().getTime())
setTimeout(function () {
console.log(1);
console.log('gsy---setTimeout', new Date().getTime())
}, 1000);
}
async function two() {
console.log('gsy---0', new Date().getTime())
setTimeout(await
function () {
console.log(2);
console.log('gsy---setTimeout', new Date().getTime())
}, 3000);
}
async function three() {
console.log('gsy---0', new Date().getTime())
setTimeout(await
function () {
console.log(3);
console.log('gsy---setTimeout', new Date().getTime())
}, 4000);
}
async function run() {
var p1 = await one();
var p2 = await two();
var p3 = await three();
}
run();
Copy the code3. Prototype chain and this
- Window. The name assignment
Window.name is a default window property of type “string” and its type cannot be changed. That is, if a value is assigned to it, the value must be of type string, otherwise the toString method of the value will be called automatically to convert the value toString.
- The body of the function
- call
// The output is string typeof window.name // Change its type to number window.name = 100 // Still output is string typeof window.nameCopy the codewindow.name = 10
function Foo() {
this.name = 'bar'
}
Foo.prototype.getName = ()=> {
console.log(this)
return this.name+1
}
let foo = new Foo();
let getName = foo.getName;
console.log(getName)
// // ()=> {
// debugger
// console.log(this)
// return this.name+1
// }
console.log(getName())
// window
// 101
console.log(getName.call(Foo))
// window
// 101
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getName = function(){ console.log(1); };
return this;
}
Foo.getName = function() { console.log(2); };
Foo.prototype.getName = function(){ console.log(3); };
var getName = function() { console.log(4); };
function getName(){ console.log(5); }
Foo.getName(); //
getName(); //
Foo().getName(); //
getName(); //
new Foo.getName(); //
new Foo().getName(); //
Copy the code4, ‘abbbaca’=>’ aACA ‘=>’ca’
- Stack on stack on stack
- The pointer moves to a different position
- Static method of string length
//// 'abbbaca'=>' aACA '=>'ca' /** * Remove adjacent characters that appear more than = 2 times * @param {string}s */ let removeDuplicate =(s) =>{const stack = [] // Space: O(n) let top let next let i = 0 while (i < s.length) { // Time: O(n) top = stack[stack.length-1] next = s[I] if (next === top) { // 2. Move pointer, Pop () while (s[I] === top) I += 1} else {stack.push(next) I += 1}} return stack.join(" ") // Time: O(n) } let s = 'abbbaca' let b = removeDuplicates(s) console.log(b)Copy the code- No pointer movement
// 'abbaca'=>'aaca'=>'ca'
// 'abbbaca'=>'abaca'
var removeDuplicates = function(S) {
let stack = [S[0]]
for (let i = 1; i < S.length; i++) {
if (S[i] === stack[stack.length - 1]) {
stack.pop()
} else {
stack.push(S[i])
}
}
return stack.join('')
};
let s = 'abbbaca'
let b = removeDuplicates(s)
console.log(b)
Copy the code//// 'abbbaca'=>'aaca'=>'ca' let s = 'abbbbaca' const removeDuplicates = function (s) { let arr = s.split('') let newArr = arr while (quDouble(newArr).flag) { newArr = quDouble(newArr) } return newArr.arr.join('') }; function quDouble(arr) { debugger let minidx = 0 let flag = false for (let i = 0; i < arr.length; i++) { minidx = i let j = i while (arr[i] === arr[j + 1]) { flag = true; j++ } if (i ! == j) { arr.splice(i, j-i+1) } } return { arr: arr, flag: flag }; } let newString = removeDuplicates(s) console.log(newString)Copy the code