在typescript中定义对象键的类型

我是typescript新手,我想为我的对象键定义类型,我已经检查了一些方法来实现它,但是在分配不同类型的值时不会抛出错误。例如

interface sectionProp { 
    _type1: String,
    _columnStrechAllowed: Boolean,
    _columnOccupancy: Number,
    is_mandatory: Boolean
}


export class sectionProperties {
  folioSectionContentProp = <sectionProp> {}

  constructor(type?) {
    this.folioSectionContentProp._type1 = type;
    this.folioSectionContentProp._columnStrechAllowed = false;
    this.folioSectionContentProp._columnOccupancy = 6;
    this.folioSectionContentProp.is_mandatory = false;
  }

}

export class createNewSection extends sectionProperties {
  constructor() {
    super("Test") // here I will assign value
 // super(12)     //@ this does not generate any error as well
 // I might assign value by some other way (from object creation) 
 // but I want to know the reason if type is defined then it should 
 // not accept any value other than type 
  }

}

var z = new createNewSection();
console.log(z)

PS:我想定义我的对象键类型

谢谢